INSTRUCCIONES:
1.No imprimas las 90 preguntas.
2. Trata de contestarlas usando tus notas, libros y Blog.
3. Pregunta a tus compañeros y/o profesor por aquellas en las que tengas dudas.
4. Úsalas para prepararte para tu examen bimestral.
QUIZ 01. MOVIMIENTO (DESCRICPIÓN Y MEDICIÓN)
Alumn@: ___________________________________________ Calif.: _____
I. Relaciona el concepto con las siguientes oraciones:
Estroboscopio; Títere; Móvil; Movimiento; Los ojos
Sentidos; Movimiento de un colibrí; Movimiento de las estrellas; Cámara de video; Movimiento del viento; Estetoscopio; Telescopio;
1.Es el cambio de posición de un cuerpo con respecto al tiempo. _____________________________
2.Así se le conoce en Física a un objeto que se mueve o que puede moverse. _________________________
3.Son el medio de contacto con el mundo; gracias a ellos percibimos los objetos que en él existen y también sus cambios y movimientos. _______________________
4.Requiere de mucho tiempo para percibirse. __________________________
5.No podemos verlo, pero sentimos sus efectos. ________________________
6.Aparato inventado por el ser humano para contrarrestar la limitante de sus sentidos. Nos permite apreciar el movimiento de un órgano invisible de nuestro cuerpo. _______________________
7.Instrumento que nos permite apreciar movimientos demasiado rápidos para la vista (como el movimiento de un colibrí). __________________________
II.Selecciona la respuesta correcta:
8.Es un cambio en la posición de un cuerpo con respecto a un punto de referencia
A) Movimiento B) Trayectoria C) Velocidad D)Aceleración
9.En un día lluvioso, a través de nuestros sentidos podemos percibir el movimiento de: las hojas de los árboles, las nubes, los pájaros, el correr del agua sobre el suelo, la luz y el sonido de viento; es decir, cuando cambian los cuerpos de lugar en un determinado lapso de:
A) Tiempo B) Clima C) Estación D) Espacio
10.¿Cómo sabemos que un avión se acerca o se aleja, aún sin mirarlo?
A) No podemos verlo, pero sí escuchar los sonidos que emite.
B) Sabemos que se mueve porque la intensidad del sonido que emite varía a transcurrir el tiempo
C) Cuanto más intenso sea el sonido percibido, más cerca de nosotros se encuentra el avión.
D) Todas las anteriores.
III.Resuelve el siguiente problema
11.Una pelota se lanza hacia arriba a una velocidad de 60 m/s. La ecuación para calcular su altura en un tiempo determinado está dada por: h= 60t – 5t2. Calcule su altura a los 2 segundos después de haber sido lanzada.
QUIZ 02. PUNTO DE REFERENCIA Y TRAYECTORIA
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.Un ejemplo de un buen punto de referencia es:
A) Mariposa B) Auto C) Un edificio D) Un perro
2.El movimiento depende del punto de referencia que se considere para describirlo. Por eso decimos que el movimiento es:
A) Definido B) Variable C) Relativo D) Indefinido
3.Línea recta o curva que describe la ruta seguida por un objeto en movimiento (un meteoro en la atmósfera, un planeta alrededor del sol, un proyectil disparado por un cañón, o un cohete en vuelo)
A) Movimiento B) Trayectoria C) Velocidad D) Aceleración
4.Para describir con precisión algún fenómeno de la naturaleza, primero necesitamos: observarlo y medirlo; es decir, conocer su:
A) Forma B) Característica C) Magnitud D) Estructura
5.Es el más sencillo de todos los tipos de movimiento
A) Circular B) Parabólico C) Rectilíneo D) Caída libre
6.Unidad fundamental para representar la distancia de acuerdo al Sistema Internacional
A) metro / segundo B) kilómetro C) metro D) pie
7.Sistema de unidades usado por las relaciones entre los países, como los negocios que tienen entre sí y para poder comunicarse mejor.
A) Internacional B) Inglés C) Mexicano D) Universal
8.Una persona mide 6 pies y 5 pulgadas. ¿Cuál es su altura en metros?
A) 1.95 m B) 1.84 m C) 1.83 m D) 1.85 m
9.La distancia promedio entre la Tierra y el Sol es de 150 000 000 000 m, ¿cómo se escribe esta distancia en notación científica?
A) 0.150 X 1012 m B) 15.0 X 1010 m C) 1.50 X 1011 m D) 150 X 109 m
10.Diversas trayectorias.
Tracen la trayectoria que sigue el punto de cada figura en el movimiento que se observa. Escriban en la línea la letra que corresponde a los siguientes tipos de movimiento:
1. Rectilíneo: ____________
2. Circular: ____________
3. Elíptico: ____________
4. Vibratorio: ____________
5. Parabólico: ____________
6: Oscilatorio:____________
7: Rotacional: ____________
QUIZ 03. RAPIDEZ Y VELOCIDAD
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.Cambio de dirección de un cuerpo en relación con el tiempo, sin considerar su dirección:
A) Velocidad B) Aceleración C) Desplazamiento D) Rapidez
2.Cambio de posición de un cuerpo con respecto al tiempo considerando su dirección.
A) Velocidad B) Aceleración C) Desplazamiento D) Rapidez
3.Solamente rapidez y velocidad significan lo mismo, cuando el desplazamiento de un objeto móvil mantiene un movimiento:
A) Rectilíneo uniforme B) Parabólico C) En caída libre D) Acelerado
4.Si la velocidad bajo tierra del topo es de 0.01 km/h, ¿a cuántos m/s equivale?
A) 0.002 m/s B) 0.02 m/s C) 0.04 m/s D) 360 m/s
5.Se dice que la luz viaja a 300,000 Km/s y que el sonido lo hace a 300 m/s. ¿Quién llegará primero hasta donde tú estás: la luz o el sonido?
A) Ambas llegan al mismo tiempo.
B) Primero llegará el sonido, porque se propaga en forma de onda.
C) Primero llegará la luz, porque viaja a mayor velocidad que el sonido.
D) Primero llega la luz, porque viaja en forma de ondas.
6.Dos objetos que viajan a la misma rapidez tienen diferentes velocidades si
A)Comienzan en diferentes tiempos
B)Viajan distancias diferentes
C)Se mueven en diferentes direcciones
7.Pepe camina 2 km, pero no indicamos hacia dónde, hablamos de una magnitud
A) Vectorial B) Escalar C) No dirigida D) Dirigida
8.El decir 25 km/hr hacia el norte se refiere a:
A) Magnitud Vectorial B) Magnitud Escalar C) Magnitud D) Medición
9.Un carro recorre una distancia de 82 kilómetros en 2 horas. Calcule la velocidad en m/s.
10.Un carro se mueve con una velocidad constante de 10 m/s. Grafique el movimiento del objeto durante los primeros 5 segundos. Recuerda que distancia=velocidad*tiempo
11. Pepe sale de paseo. Pepe fue a dar una vuelta. ¿Qué indica la flecha que apunta hacia la derecha, la trayectoria o el desplazamiento? Explique.
QUIZ 04. GRÁFICAS DE VELOCIDAD VS TIEMPO
Alumn@: ___________________________________________ Calif.: _____
I. Selecciona la respuesta correcta:
1. En una gráfica distancia vs tiempo, si resulta una línea recta inclinada, la velocidad…
A) Disminuye B) Crece C) Es constante D) No existe
2.Isabel e Inés grafican la velocidad de reacción del cloruro de potasio y del cloruro de sodio a diferentes temperaturas. ¿Cuál de las siguientes opciones describe correctamente el comportamiento de ambas sustancias durante el incremento de temperatura?
A) La velocidad de reacción del cloruro de sodio aumenta conforme aumenta la temperatura.
B) La velocidad de reacción del cloruro de potasio disminuye conforme aumenta la temperatura.
C) La velocidad de reacción del cloruro de sodio y potasio es igual al aumentar la temperatura.
D) La velocidad de reacción es mayor en el cloruro de potasio que en el cloruro de sodio al aumentar la temperatura
3.¿Qué tipo de gráfica no puedes usar para analizar la aceleración de un cuerpo? A) Distancia contra tiempo B) Movimiento contra tiempo
C) Velocidad contra tiempo
4.¿Qué indica la pendiente de una gráfica distancia-tiempo?
A) Velocidad B) Aceleración C) Desplazamiento D) Rapidez
5.Describe el movimiento de un niño que sigue las instrucciones de su profesor en una práctica de educación física. Usa correctamente los conceptos de distancia, tiempo, velocidad y aceleración.
6. Bailando un vals
Describe el movimiento de una muchacha que está ensayando para sus XV años. Para ello use los conceptos físicos visto en clase: punto de referencia, desplazamiento y velocidad.
QUIZ 05. CAÍDA LIBRE
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.Los paracaidistas al momento de saltar lo hacen en una forma de movimiento llamado:
A) Rectilíneo B) Ondulatorio C) Parabólico D) Caída libre
2.Movimiento que está sometido únicamente a la acción de la fuerza de gravedad
A) Fricción B) Gravitacional C) Caída libre D) Uniforme
3.¿De qué tipo es el movimiento de los cuerpos que caen, según Galileo Galilei?
A) Rectilíneo uniforme B) Parabólico C) Ondulatorio D) Caída libre
4.Una de las principales aportaciones de Galileo sobre la caída libre de los cuerpos, fue que la distancia recorrida:
A) Es proporcional al cuadrado del tiempo transcurrido.
B) Es igual al tiempo transcurrido.
C) No influye con el tiempo transcurrido.
D) Es proporcional a la velocidad
5.¿Qué sucederá si dejamos caer una pluma y una piedra en un recipiente libre de aire (al vacío), en donde no haya rozamiento ni fricción?
A) Llega primero la pluma B) Llega primero la piedra
C) Llegan al mismo tiempo D) Flotan en el aire
6.Científico italiano que realizó experimentos en la torre de Pisa para comprobar la caída libre de los cuerpos
A) Aristóteles B) Newton C) Galileo D) Copérnico
7.Personaje cuyas explicaciones acerca del movimiento estaban sustentadas en la experimentación y el tratamiento matemático, más que en sólo ideas y lógica.
A) Galileo Galilei B) Newton C) Aristóteles D) Platón
8.Si una canica tarda 18 segundos en caer con una aceleración de 9.81 m/s2. ¿Qué velocidad lleva al caer al piso?
9.Desde lo alto de un edificio de 15 metros de altura se deja caer una bola de boliche. Si consideramos que cae libremente, ¿cuánto tiempo tardará en llegar al suelo?
10.Completa la siguiente tabla:
Aristóteles
Explicación elaborada acerca de la caída de los cuerpos.
Galileo
Recursos utilizados para apoyar construir sus explicaciones
QUIZ 06. ACELERACIÓN CONSTANTE
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.Cambio de velocidad de un cuerpo en un cierto tiempo
A) Velocidad B) Aceleración C) Desplazamiento D) Rapidez
2.Al viajar en una bicicleta, si acelero, me permitirá recorrer en menor tiempo una:
A) Menor distancia B) Igual distancia
C) Mayor distancia D) Mayor o igual distancia.
3.Un auto que inicialmente viaja a 10 m/s aumenta su rapidez a 30 m/s en 5 segundos. ¿Cuál es el valor de la aceleración del carro?
Fórmula aceleración = (Velocidad final – Velocidad inicial) / tiempo
A) +4 m/s2 B) -4 m/s2 C) 4 m/s D) 8 m/s2
4.Un tren viaja en línea recta a 10 m/s y acelera durante 4 seg. alcanzando una velocidad de 20 m/s, ¿cuál es el valor de su aceleración? a = (Vf – Vi)/t
A) 2.5 m/s2 B) 5 m/s2 C) 7.5 m/s2 D) 10.0 m/s2
5.Una pelota se deja caer desde un edificio y tarda 5 segundos. ¿Cuál es la altura del edificio? Fórmula: h = ½ g t2 = 4.9*t2
A) 4.9 m B) 24.5 m C) 122.5 m D) 9.8 m
6.¿Cuáles son las variables que se utilizan en una gráfica para determinar la aceleración de un objeto?
A) Velocidad y tiempo B) Altura y tiempo C) Distancia y tiempo D) Ninguna
7.Un insecto aterriza sobre un disco compacto que está puesto sobre el reproductor. Si el insecto gira con el disco, entonces está…
A) Acelerando B) Desacelerando
C) Sin aceleración D) Velocidad constante
8.Al ir en bicicleta, Mariana lleva una velocidad de 12 m/s y al llegar a una calle que está en bajada, en 4 segundos su velocidad pasa a 36 m/s, ¿cuál fue la aceleración que alcanzó?
9.¿Cuáles son las tres formas en que un objeto puede acelerar?
A)Incrementar velocidad, disminuir velocidad o cambiar dirección
B)Incrementar el tiempo, disminuir el tiempo o cambiar velocidad
C)Incrementar desplazamiento, tiempo y velocidad
10.Describe el movimiento del balín que se mueve sobre un eje de coordenadas. Los números sobre el balín representan los tiempos en segundos
QUIZ 07. MOVIMIENTO DE ONDAS MECÁNICAS
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.El sonido del avión lo podemos percibir porque se propaga a través del aire en forma de:
A) Radiaciones B) Ondas mecánicas C) Ondas ElectroMag D) Rayos
2.Es una perturbación que transfiere energía de un lugar a otro y son producidas cuando una fuente causa que un medio vibre.
A) Onda B) Sonido C) Luz D) Aire
3.¿Qué característica de una onda de sonido es afectada por el efecto Doppler?
A) Longitud de onda B) Frecuencia. C) Velocidad. D) Amplitud.
4.La luz, las olas del mar y el sonido del viento se transmiten en el espacio a través de:
A) Ondas B) Impulsos C) Radiaciones D) Emisiones
5.Las ondas mecánicas como el sonido necesitan un medio para propagarse. El sonido no se propaga en:
A) Los gases B) Los sólidos C) Los líquidos D) El vacío
6.Ondas que se forman si las partículas del medio vibran en forma paralela a la dirección de propagación de la onda, tal como se da con el movimiento de los resortes y el sonido.
A) Largas B) Longitudinales C) Transversales D) Cortas
7.Ondas que se forman si las partículas del medio vibran en forma perpendicular a la dirección de la propagación de la onda, como en las olas del mar y el movimiento de una cuerda.
A) Largas B) Longitudinales C) Transversales D) Cortas
8.Es la distancia entre dos crestas o dos valles consecutivos.
A) Cresta B) Longitud de onda C) Periodo D) Valle
9.Es la unidad de frecuencia en el movimiento ondulatorio
A) metro B) litro C) Hertz D) m/s
10.Señala en un dibujo los elementos de la siguiente onda:
A) Cresta B) Longitud de onda C) Periodo D) Valle
QUIZ 08. EL CAMBIO Y LAS INTERACCIONES
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.Es necesario/a para que se produzca un cambio en la naturaleza.
A) Interacción B) Intención C) Energía D) Masa
2.Son las causantes tanto de que las cosa empiecen a moverse, como de que se detengan:
A) Aire B) movimiento C) las fuerzas D) energía
3.Según Newton, las interacciones que se ejercen sobre los cuerpos permiten que tengan un cambio en su posición o en su:
A) Estructura B) Forma C) Magnitud D) Intensidad
4.Son interacciones que se ejercen sobre los cuerpos, permite que tengan un cambio en su posición o en su forma, Newton las denomino:
A) Temperaturas B) Frecuencias C) Tensiones D) Fuerzas
5.¿Cuál es el resultado de las interacciones entre el cuerpo del atleta y las pesas al intentar levantarlas?
A) Una marca olímpica B) Un esfuerzo
C) Cambio en estado de movimiento D) Aumento en la masa muscular
6.La interacción que realizan tres hombres al jalar una piedra, representa:
A) Suma de fuerza B) Mayor fuerza
C) 3 Movimientos diferentes D) Inmovilidad
7.En el béisbol, el tenis o el boxeo, el tipo de fuerzas que interaccionan son de:
A) Contacto B) Atracción C) Distancia D) Repulsión
8.Las fuerzas como la fricción, un empujón o jalar un objeto se clasifican:
A) De contacto B) A distancia C) Fundamentales D) Básicas
9.Cómo se le llama a la fuerza que ejerce el imán sobre un objeto:
A) De contacto B) estática C) A distancia D) dinámica
10.Relaciona las columnas de cambios de movimiento y la de fuerzas, e identifica si la fuerza que causa el cambio del movimiento es de contacto o de distancia
a)Hoja de árbol suelta que baja y sube Contacto con piso
b)Pelota que sube y baja Eléctrica
c)Papelito que sube hacia una regla de plástico Contacto con pared
d)Rana que salta Contacto con techo
e)Clip que inicia movimiento sobre mesa horizontal Peso
f)Bola de chicle que sube y se queda detenida Contacto con cuerda
g)Pelota que cambia el sentido de su movimiento Contacto con piso
h)Perro que corre y se queda detenido. Magnética
i)Moneda que se desliza y se detiene Contacto con aire
QUIZ 09. LA IDEA DE FUERZA
Alumn@: ___________________________________________ Calif.: _____
I.Selecciona la respuesta correcta:
1.Un oficinista empuja una caja registradora con ambas manos. ¿Qué sistema de fuerzas ejerce con sus manos?
A) Fuerzas paralelas B) Fuerzas concurrentes
C) Fuerzas colineales D) Fuerzas resultantes
2.Sistema de fuerzas que comparten la misma línea de acción. Pueden actuar en la misma dirección o en direcciones opuestas.
A) Paralelas B) Concurrentes C) Colineales D) Conjuntas
3.Las fuerzas pueden representarse por su magnitud, dirección y sentido en un plano cartesiano mediante:
A) Vectores B) Ecuaciones C) Escalares D) Líneas
4.¿Cuáles son las características de la fuerza como una magnitud vectorial?
A) Magnitud, dirección y sentido.
B) Traslación, rotación y precesión.
C) Inclinación, intensidad y orientación.
D) Origen, ordenada y abscisa.
5.Un barco es remolcado por otros dos. En la figura observamos que la fuerza resultante es __________ las fuerzas individuales.
A) Mayor que B) Menor que
C) Igual a D) Diferente a
6.El movimiento de los planetas, alrededor del sol y sobre su propio eje, así como los terremotos o los tsunamis, son el resultado de las interacciones entre fuerzas, que en el SIU su unidad de medida es:
A) El kilogramo B) El Joule D) El ampere D) Newton
7.Debido a que la fuerza requiere que se le indique dirección de aplicación (como el desplazamiento y la velocidad), éstas entran en la categoría de:
A) Vectores B) Escalares C) Nominales D) Superiores
8.Cuando un cuerpo es sometido a varias fuerzas, la suma vectorial de las mismas fuerzas es conocida como fuerza…
A) Sumatoria B) Resultante C) Total D) Centrípeta
9.Cuando la fuerza resultante de un sistema es cero, decimos que:
A) No hay fuerza B) Desequilibrio C) Hay equilibrio D) constante
10.Unidad fundamental para medir las fuerzas en el Sistema Internacional
A) Newton B) Joule C) Kg D) Libra
11.Supón que tres personas que jalan el coche hacia la izquierda lo hacen con una fuerza de 70 N, 35 N y 52.5 N respectivamente y que son las únicas fuerzas que actúan.
a.¿Cuál es la magnitud de la fuerza resultante?
b.¿Cuál será su dirección en referencia a las fuerzas aplicadas?
lunes, 24 de octubre de 2011
miércoles, 19 de octubre de 2011
Study for Quiz October 24
Here you can find the questions for preparing your 2nd and final quiz of October. GRAPHS AND FORCES. Remeber to ANSWER THE QUESTIONS IN ENGLISH.
You can ask for help tomorrow in the break or on friday in the class.
Consider attending to "ASESORÍA" this friday at 4:00 PM.
Describiendo el movimiento con gráficas
1.¿Cuáles son los tipos de gráficas que puedes usar para analizar la velocidad y aceleración de un objeto?
2.¿Qué muestra la pendiente de la recta de una gráfica distancia vs tiempo acerca del movimiento del objeto?
3.¿Qué representa la pendiente de una gráfica velocidad vs tiempo?
4.¿Cómo se representa la velocidad de un cuerpo y sus cambios?
5.¿Qué es el movimiento rectilíneo uniforme?
6.Representa en una gráfica el aumento en la velocidad con respecto al tiempo de un objeto.
7.Representa un objeto que va disminuyendo su velocidad con respecto al tiempo.
8.La “elevación” de una línea en una gráfica distancia vs tiempo es de 600 metros y el “recorrido” es de 3 minutos. ¿Cuál es la pendiente de la línea? ¿Cuál es el valor de la velocidad?
9.¿Cuál es la diferencia entre movimiento rectilíneo uniforme y movimiento rectilíneo con aceleración constante?
10.¿Cuál es la velocidad de un objeto si en la gráfica de posición-tiempo de un objeto en un plano inclinado, la recta que relaciona ambas magnitudes es horizontal?
Entra a http://www.educaplus.org/movi/3_3et1.html y continúa tu estudio sobre los conceptos relacionados con el movimiento. Enfócate en el movimiento rectilíneo uniforme.
Fuerzas
1.¿Existe un objeto que no esté sometido a la acción de otro?
2.¿Qué es una fuerza? ¿Es vector o escalar?
3.¿Cuáles son los dos principales efectos de las fuerzas? Mencione tres ejemplos de cada uno.
4.¿En qué unidades se miden las fuerzas?
5.Menciona tres ejemplos de fuerzas a distancia y fuerzas por contacto.
6.¿Cómo se pueden representar las fuerzas?
7.¿Qué es una fuerza resultante?
8.¿Cuándo un objeto está en reposo, no hay fuerzas actuando sobre él?
9.¿Cuáles son las fuerzas balanceadas? Da un ejemplo.
10.¿Cuáles son las fuerzas no balanceadas? Da un ejemplo.
Describing motion with graphs
1.What are the type of graphs that you can use to analyze the velocity and acceleration of an object?
2.What does the slope of a distance vs time graph show us about the motion of an object?
3.What does the slope of a velocity vs time graph represent?
4.How do you represent the velocity of an object and its changes?
5.What is uniform rectilinear motion?
6.Show an object that is speeding up over the time (use distance vs time and velocity vs time graphs)
7.Show an object that is slowing down over the time (use distance vs time and velocity vs time graphs)
8.The rise equals 600 meters and the run equals 3 minutes in a distance vs time graph. What is the value of the slope? What is the velocity?
9.What is the difference between uniform rectilinear motion and constant acceleration rectilinear motion?
10.What is the velocity of an object if the distance vs time graph shows a horizontal line?
Forces
1.Is there any object that is not under the action of another?
2.What is a force? ¿Is it a vector or a scalar?
3.What are the main effects of the forces? Give three examples of each.
4.What are the units to measure force?
5.Give three examples of distance and contact forces.
6.If forces are vectors, how can we represent forces?
7.What is Resultant force (Net force)?
8.When an object is at repose, are there forces acting upon it?
9.What are balanced forces? Give one example.
10.What are unbalanced forces? Give one example.
You can ask for help tomorrow in the break or on friday in the class.
Consider attending to "ASESORÍA" this friday at 4:00 PM.
Describiendo el movimiento con gráficas
1.¿Cuáles son los tipos de gráficas que puedes usar para analizar la velocidad y aceleración de un objeto?
2.¿Qué muestra la pendiente de la recta de una gráfica distancia vs tiempo acerca del movimiento del objeto?
3.¿Qué representa la pendiente de una gráfica velocidad vs tiempo?
4.¿Cómo se representa la velocidad de un cuerpo y sus cambios?
5.¿Qué es el movimiento rectilíneo uniforme?
6.Representa en una gráfica el aumento en la velocidad con respecto al tiempo de un objeto.
7.Representa un objeto que va disminuyendo su velocidad con respecto al tiempo.
8.La “elevación” de una línea en una gráfica distancia vs tiempo es de 600 metros y el “recorrido” es de 3 minutos. ¿Cuál es la pendiente de la línea? ¿Cuál es el valor de la velocidad?
9.¿Cuál es la diferencia entre movimiento rectilíneo uniforme y movimiento rectilíneo con aceleración constante?
10.¿Cuál es la velocidad de un objeto si en la gráfica de posición-tiempo de un objeto en un plano inclinado, la recta que relaciona ambas magnitudes es horizontal?
Entra a http://www.educaplus.org/movi/3_3et1.html y continúa tu estudio sobre los conceptos relacionados con el movimiento. Enfócate en el movimiento rectilíneo uniforme.
Fuerzas
1.¿Existe un objeto que no esté sometido a la acción de otro?
2.¿Qué es una fuerza? ¿Es vector o escalar?
3.¿Cuáles son los dos principales efectos de las fuerzas? Mencione tres ejemplos de cada uno.
4.¿En qué unidades se miden las fuerzas?
5.Menciona tres ejemplos de fuerzas a distancia y fuerzas por contacto.
6.¿Cómo se pueden representar las fuerzas?
7.¿Qué es una fuerza resultante?
8.¿Cuándo un objeto está en reposo, no hay fuerzas actuando sobre él?
9.¿Cuáles son las fuerzas balanceadas? Da un ejemplo.
10.¿Cuáles son las fuerzas no balanceadas? Da un ejemplo.
Describing motion with graphs
1.What are the type of graphs that you can use to analyze the velocity and acceleration of an object?
2.What does the slope of a distance vs time graph show us about the motion of an object?
3.What does the slope of a velocity vs time graph represent?
4.How do you represent the velocity of an object and its changes?
5.What is uniform rectilinear motion?
6.Show an object that is speeding up over the time (use distance vs time and velocity vs time graphs)
7.Show an object that is slowing down over the time (use distance vs time and velocity vs time graphs)
8.The rise equals 600 meters and the run equals 3 minutes in a distance vs time graph. What is the value of the slope? What is the velocity?
9.What is the difference between uniform rectilinear motion and constant acceleration rectilinear motion?
10.What is the velocity of an object if the distance vs time graph shows a horizontal line?
Forces
1.Is there any object that is not under the action of another?
2.What is a force? ¿Is it a vector or a scalar?
3.What are the main effects of the forces? Give three examples of each.
4.What are the units to measure force?
5.Give three examples of distance and contact forces.
6.If forces are vectors, how can we represent forces?
7.What is Resultant force (Net force)?
8.When an object is at repose, are there forces acting upon it?
9.What are balanced forces? Give one example.
10.What are unbalanced forces? Give one example.
lunes, 17 de octubre de 2011
EL ABC DEL APRENDIZAJE
"Es verdad que ninguna disciplina al momento de recibirla, parece agradable, sino más bien causa de tristeza; sin embargo, después produce fruto de justicia y paz para quienes han sido entrenados por ella"
La Biblia
A punta con atención el tema nuevo.
B log para completar tus notas.
C ontesta Ejercicios, Repaso (Gánate 1 punto) y Tarea Extra.
D udas se resuelve en Asesoría (Viernes ANDES)
É xito en el examen quincenal.
¿Cómo impacta en mi calificación?
APUNTA
*Ponga el título y fecha con rojo, tome nota de lo más relevante.
*Su participación hace la diferencia entre una clase aburrida y una interesante.
BLOG
*Si no considera los ejemplos, ejercicios, imágenes y conclusiones del Blog para completar sus notas se calificará su cuaderno sobre 8
*(En Noviembre será sobre 7, en diciembre será sobre 6, etc.)
CONTESTA
*Todos los días deberá llevarse su cuaderno de ejercicios para trabajar en su TAREA 15 minutos diarios en casa.
*Por ningún motivo lo deje en su casillero.
* El REPASO es REQUISITO PARA PODER PRESENTAR EXAMEN (Esto está autorizado por Coordinación de Secundaria)
* La TAREA EXTRA es otra manera de ganar puntos y resolver problemas más difíciles. La Tarea extra es opcional para Ciencias 2 y Mate 2.
DUDAS
*El estudiante tiene el derecho de una asesoría PREVIA AL EXAMEN.
*Estudiante que reprueba un examen anterior está obligado a asistir a asesoría.
* Todos los estudiantes de Mate 2 (excepto las cuatro alumnas más responsables el grupo) están obligados a ir a asesoría.
* En caso de no poder ir a asesoría, debe presentar un justificante con nombre y firma del padre de familia y el REPASO RESUELTO el día de la asesoría por la mañana. De otro modo, pierde el punto y el derecho a presentar examen.
ÉXITO
* Los exámenes ya no serán semanales, sino quincenales.
* El profesor se compromete a respaldar el trabajo de cualquier alumno que se someta a este proceso.
Les deseo éxito y que Dios bendiga todo su trabajo y esfuerzo.
De antemano, muchas gracias por su esfuerzo.
Prof. Amir Madrid
Comentarios. amirmkt@yahoo.com.mx
La Biblia
A punta con atención el tema nuevo.
B log para completar tus notas.
C ontesta Ejercicios, Repaso (Gánate 1 punto) y Tarea Extra.
D udas se resuelve en Asesoría (Viernes ANDES)
É xito en el examen quincenal.
¿Cómo impacta en mi calificación?
APUNTA
*Ponga el título y fecha con rojo, tome nota de lo más relevante.
*Su participación hace la diferencia entre una clase aburrida y una interesante.
BLOG
*Si no considera los ejemplos, ejercicios, imágenes y conclusiones del Blog para completar sus notas se calificará su cuaderno sobre 8
*(En Noviembre será sobre 7, en diciembre será sobre 6, etc.)
CONTESTA
*Todos los días deberá llevarse su cuaderno de ejercicios para trabajar en su TAREA 15 minutos diarios en casa.
*Por ningún motivo lo deje en su casillero.
* El REPASO es REQUISITO PARA PODER PRESENTAR EXAMEN (Esto está autorizado por Coordinación de Secundaria)
* La TAREA EXTRA es otra manera de ganar puntos y resolver problemas más difíciles. La Tarea extra es opcional para Ciencias 2 y Mate 2.
DUDAS
*El estudiante tiene el derecho de una asesoría PREVIA AL EXAMEN.
*Estudiante que reprueba un examen anterior está obligado a asistir a asesoría.
* Todos los estudiantes de Mate 2 (excepto las cuatro alumnas más responsables el grupo) están obligados a ir a asesoría.
* En caso de no poder ir a asesoría, debe presentar un justificante con nombre y firma del padre de familia y el REPASO RESUELTO el día de la asesoría por la mañana. De otro modo, pierde el punto y el derecho a presentar examen.
ÉXITO
* Los exámenes ya no serán semanales, sino quincenales.
* El profesor se compromete a respaldar el trabajo de cualquier alumno que se someta a este proceso.
Les deseo éxito y que Dios bendiga todo su trabajo y esfuerzo.
De antemano, muchas gracias por su esfuerzo.
Prof. Amir Madrid
Comentarios. amirmkt@yahoo.com.mx
domingo, 16 de octubre de 2011
07 FORCES IN OUR ENVIRONMENT
DESCRIPTION OF FORCES IN OUR ENVIRONMENT
SEPyC Expected learning
1. Describe la fuerza como efecto de la interacción entre los objetos y la representa con vectores.
2. Aplica los métodos gráficos del polígono y paralelogramo para la obtención de la fuerza resultante que actúa sobre un objeto, y describe el movimiento producido en situaciones cotidianas.
3. Argumenta la relación del estado de reposo de un objeto con el equilibrio de fuerzas actuantes, con el uso de vectores, en situaciones cotidianas.
01 THE FORCE
Why do objects change their motion?
Why do objects change their shape?
The following illustrations show more of the effect of forces. Are you able to identify them?
1. The tennis player hits the ball away from her.
(A force can change the course (direction) of a moving object)
2. The driver uses the brakes to stop the car.
(A force can halt a moving object)
3. The force of attraction is exerted on the elastic band.
(A force change the shape of an object.)
4. The force of thrust in the same direction as the motion is exerted on the rolling ball. (A force can change the speed of a moving object)
5. The athlete swings the hammer to rotate it around him
(A force can make an object rotate )
A) What is a force? Motion Effects
A) What is a force? Shape Effects
So, what is a force?
The Meaning of Force
A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction.
*A force is the result of the interaction of one object with another object.
*Force is the external agent that changes the state of rest or uniform motion of a body along a straight line.
*A force IS NOT inside an object.
B)Classifying Forces
For simplicity sake, all forces (interactions) between objects can be placed into two broad categories:
•Contact forces, and
•forces resulting from action-at-a-Distance
CONTACT FORCES(mechanic)
Contact forces are those types of forces that result when the two interacting objects are perceived to be physically contacting each other.
Examples of contact forces include:
1. The vehicle in the illustration has broken down and cannot move by itself. The tow truck has to pull it. This car also cannot move by itself. The man has to push it.
2. When something has to be pulled or pushed, we say that we must exert force on it. You use the force of thrust to push something away from you, or the force of attraction to pull something towards you.
3. Frictional forces is the force between two objects in contact with each other. It causes moving objects to slow down. It is a resistive force.
The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it
4. Stretching - Tensional forces
The tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends. The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.
5. Rubbing
6. Air resistance forces
The air resistance is a special type of frictional force that acts upon objects as they travel through the air. The force of air resistance is often observed to oppose the motion of an object.
7. Applied forces
An applied force is a force that is applied to an object by a person or another object. If a person is pushing a desk across the room, then there is an applied force acting upon the object. The applied force is the force exerted on the desk by the person.
8. Compression
9. Normal forces
The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. On occasions, a normal force is exerted horizontally between two objects that are in contact with each other. For instance, if a person leans against a wall, the wall pushes horizontally on the person.
10. Spring Force
The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it. An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position.
DISTANCE FORCES
Action-at-a-distance forces are those types of forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation.
It is even possible to bring objects into motion or to change the direction of the motion without any contact. Forces that affect objects without making contact are identified as forces that operate over distance.
Three kinds of force can have an effect without any contact with objects:
Gravitational force (also known as Weight)
The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth.
For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation. Even when your feet leave the earth and you are no longer in physical contact with the earth, there is a gravitational pull between you and the Earth.
Magnetic force
Magnetic forces exist between magnets and other magnets, and also between magnets and magnetic materials. The force can be attraction or repulsion.
Magnetic forces are action-at-a-distance forces. For example, two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimeters. These specific forces will be discussed in more detail later in Lesson 2 as well as in other lessons.
Electrostatic force
Forces between electrical charges.
Electric forces are action-at-a-distance forces. For example, the protons in the nucleus of an atom and the electrons outside the nucleus experience an electrical pull towards each other despite their small spatial separation.
REMEMBER
A force can change the course (direction) of a moving object.
A force can halt a moving object.
A force change the shape of an object.
A force can change the speed of a moving object.
A force can make an object rotate.
02 NET FORCE
Resultant Force
Any object can be made to move by the application of force.
Many forces can act simultaneously on a body.
For example, several people can jointly move a boulder but a strong person can move the same boulder all by himself.
That is, the force applied by the strong man produces the same effect as that produced by the net force applied by all.
The force applied by the strong man is the resultant force.
03 FORCES EQUILIBRIUM
Balanced forces
If two forces that have the same magnitude & direction are applied to a body in opposite senses, this won’t move because the effects balance each other.
Forces system analysis is important when designing
Bridges
Building
Oil rigs
UNBALANCED FORCES
WHEN TWO FORCES ACT UPON EACH OTHER IN OPPOSITE DIRECTIONS, AND THEY ARE BOTH THE SAME SIZE, WE SAY THEY ARE BALANCED. YOU CAN SEE BALANCED FORCES IN A TUG-OF-WAR GAME WHEN THE ROPE IS NOT MOVING.
AN UNBALANCED FORCE ACTING ON AN OBJECT CHANGES ITS SPEED OR DIRECTION. THE RESULTANT OF UNBALANCED FORCES IS ALWAYS GREATER THAN ZERO.
THE FIGURES SHOW A BLOCK OF WOOD ON A TABLE. WHEN THE BLOCK IS PULLED AT POINT A, IT BEGINS TO MOVE TOWARDS THE LEFT AND IF THE BLOCK IS PULLED AT THE POINT B IT MOVES TOWARDS THE RIGHT.
ALL OF US KNOW THAT WHEN WE STOP PEDALLING A BICYCLE, THE SPEED OF THE BICYCLE DECREASES DUE TO THE ACTION OF FRICTION, WHICH IS THE ONLY FORCE ACTING ON THE BICYCLE. THUS, IF THE FORCES ACTING ON A BODY PRODUCE ANY CHANGE IN STATE OF REST OR MOTION, THEN THE FORCES ARE SAID TO BE UNBALANCED. AN UNBALANCED FORCE ACTING ON AN OBJECT CHANGES ITS SPEED OR DIRECTION. THE RESULTANT OF UNBALANCED FORCES IS ALWAYS GREATER THAN ZERO.
BALANCED FORCES
IF THE BLOCK IS PULLED FROM BOTH SIDES WITH THE SAME EFFORT THE BLOCK REMAINS STATIONARY. THE FORCES ARE EQUAL AND OPPOSITE AND THEREFORE THE BLOCK DOES NOT MOVE. THE RESULTANT OF THE FORCES ACTING ON THE BODY IS ZERO.
IN A GAME OF TUG OF WAR WHEN BOTH THE TEAMS PULL THE ROPE WITH EQUAL AND OPPOSITE FORCES, THEN THE ROPE REMAINS STATIONARY AS THE FORCES ACTING ON IT ARE EQUAL AND OPPOSITE AND THEIR RESULTANT IS ZERO.
SQUEEZE A RUBBER BALL BETWEEN THE PALMS OF YOUR HANDS. WHAT DO YOU OBSERVE? THE SHAPE OF THE RUBBER BALL CHANGES. THE FORCES APPLIED ON THE BALL ARE EQUAL AND OPPOSITE AND THE RESULTANT OF THESE FORCES DOES NOT MOVE THE OBJECT, INSTEAD THE OBJECT GETS DEFORMED AS LONG AS THE FORCE IS APPLIED. THIS IS A TEMPORARY DEFORMATION.
REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO
Do you want to learn more?
http://www.tutorvista.com/content/science/science-i/force-laws-motion/force-laws-motionindex.php
http://www.physicsclassroom.com/
SEPyC Expected learning
1. Describe la fuerza como efecto de la interacción entre los objetos y la representa con vectores.
2. Aplica los métodos gráficos del polígono y paralelogramo para la obtención de la fuerza resultante que actúa sobre un objeto, y describe el movimiento producido en situaciones cotidianas.
3. Argumenta la relación del estado de reposo de un objeto con el equilibrio de fuerzas actuantes, con el uso de vectores, en situaciones cotidianas.
01 THE FORCE
Why do objects change their motion?
Why do objects change their shape?
The following illustrations show more of the effect of forces. Are you able to identify them?
1. The tennis player hits the ball away from her.
(A force can change the course (direction) of a moving object)
2. The driver uses the brakes to stop the car.
(A force can halt a moving object)
3. The force of attraction is exerted on the elastic band.
(A force change the shape of an object.)
4. The force of thrust in the same direction as the motion is exerted on the rolling ball. (A force can change the speed of a moving object)
5. The athlete swings the hammer to rotate it around him
(A force can make an object rotate )
A) What is a force? Motion Effects
A) What is a force? Shape Effects
So, what is a force?
The Meaning of Force
A force is a push or pull upon an object resulting from the object's interaction with another object. Whenever there is an interaction between two objects, there is a force upon each of the objects. When the interaction ceases, the two objects no longer experience the force. Forces only exist as a result of an interaction.
*A force is the result of the interaction of one object with another object.
*Force is the external agent that changes the state of rest or uniform motion of a body along a straight line.
*A force IS NOT inside an object.
B)Classifying Forces
For simplicity sake, all forces (interactions) between objects can be placed into two broad categories:
•Contact forces, and
•forces resulting from action-at-a-Distance
CONTACT FORCES(mechanic)
Contact forces are those types of forces that result when the two interacting objects are perceived to be physically contacting each other.
Examples of contact forces include:
1. The vehicle in the illustration has broken down and cannot move by itself. The tow truck has to pull it. This car also cannot move by itself. The man has to push it.
2. When something has to be pulled or pushed, we say that we must exert force on it. You use the force of thrust to push something away from you, or the force of attraction to pull something towards you.
3. Frictional forces is the force between two objects in contact with each other. It causes moving objects to slow down. It is a resistive force.
The friction force is the force exerted by a surface as an object moves across it or makes an effort to move across it
4. Stretching - Tensional forces
The tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting from opposite ends. The tension force is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.
5. Rubbing
6. Air resistance forces
The air resistance is a special type of frictional force that acts upon objects as they travel through the air. The force of air resistance is often observed to oppose the motion of an object.
7. Applied forces
An applied force is a force that is applied to an object by a person or another object. If a person is pushing a desk across the room, then there is an applied force acting upon the object. The applied force is the force exerted on the desk by the person.
8. Compression
9. Normal forces
The normal force is the support force exerted upon an object that is in contact with another stable object. For example, if a book is resting upon a surface, then the surface is exerting an upward force upon the book in order to support the weight of the book. On occasions, a normal force is exerted horizontally between two objects that are in contact with each other. For instance, if a person leans against a wall, the wall pushes horizontally on the person.
10. Spring Force
The spring force is the force exerted by a compressed or stretched spring upon any object that is attached to it. An object that compresses or stretches a spring is always acted upon by a force that restores the object to its rest or equilibrium position.
DISTANCE FORCES
Action-at-a-distance forces are those types of forces that result even when the two interacting objects are not in physical contact with each other, yet are able to exert a push or pull despite their physical separation.
It is even possible to bring objects into motion or to change the direction of the motion without any contact. Forces that affect objects without making contact are identified as forces that operate over distance.
Three kinds of force can have an effect without any contact with objects:
Gravitational force (also known as Weight)
The force of gravity is the force with which the earth, moon, or other massively large object attracts another object towards itself. By definition, this is the weight of the object. All objects upon earth experience a force of gravity that is directed "downward" towards the center of the earth.
For example, the sun and planets exert a gravitational pull on each other despite their large spatial separation. Even when your feet leave the earth and you are no longer in physical contact with the earth, there is a gravitational pull between you and the Earth.
Magnetic force
Magnetic forces exist between magnets and other magnets, and also between magnets and magnetic materials. The force can be attraction or repulsion.
Magnetic forces are action-at-a-distance forces. For example, two magnets can exert a magnetic pull on each other even when separated by a distance of a few centimeters. These specific forces will be discussed in more detail later in Lesson 2 as well as in other lessons.
Electrostatic force
Forces between electrical charges.
Electric forces are action-at-a-distance forces. For example, the protons in the nucleus of an atom and the electrons outside the nucleus experience an electrical pull towards each other despite their small spatial separation.
REMEMBER
A force can change the course (direction) of a moving object.
A force can halt a moving object.
A force change the shape of an object.
A force can change the speed of a moving object.
A force can make an object rotate.
02 NET FORCE
Resultant Force
Any object can be made to move by the application of force.
Many forces can act simultaneously on a body.
For example, several people can jointly move a boulder but a strong person can move the same boulder all by himself.
That is, the force applied by the strong man produces the same effect as that produced by the net force applied by all.
The force applied by the strong man is the resultant force.
03 FORCES EQUILIBRIUM
Balanced forces
If two forces that have the same magnitude & direction are applied to a body in opposite senses, this won’t move because the effects balance each other.
Forces system analysis is important when designing
Bridges
Building
Oil rigs
UNBALANCED FORCES
WHEN TWO FORCES ACT UPON EACH OTHER IN OPPOSITE DIRECTIONS, AND THEY ARE BOTH THE SAME SIZE, WE SAY THEY ARE BALANCED. YOU CAN SEE BALANCED FORCES IN A TUG-OF-WAR GAME WHEN THE ROPE IS NOT MOVING.
AN UNBALANCED FORCE ACTING ON AN OBJECT CHANGES ITS SPEED OR DIRECTION. THE RESULTANT OF UNBALANCED FORCES IS ALWAYS GREATER THAN ZERO.
THE FIGURES SHOW A BLOCK OF WOOD ON A TABLE. WHEN THE BLOCK IS PULLED AT POINT A, IT BEGINS TO MOVE TOWARDS THE LEFT AND IF THE BLOCK IS PULLED AT THE POINT B IT MOVES TOWARDS THE RIGHT.
ALL OF US KNOW THAT WHEN WE STOP PEDALLING A BICYCLE, THE SPEED OF THE BICYCLE DECREASES DUE TO THE ACTION OF FRICTION, WHICH IS THE ONLY FORCE ACTING ON THE BICYCLE. THUS, IF THE FORCES ACTING ON A BODY PRODUCE ANY CHANGE IN STATE OF REST OR MOTION, THEN THE FORCES ARE SAID TO BE UNBALANCED. AN UNBALANCED FORCE ACTING ON AN OBJECT CHANGES ITS SPEED OR DIRECTION. THE RESULTANT OF UNBALANCED FORCES IS ALWAYS GREATER THAN ZERO.
BALANCED FORCES
IF THE BLOCK IS PULLED FROM BOTH SIDES WITH THE SAME EFFORT THE BLOCK REMAINS STATIONARY. THE FORCES ARE EQUAL AND OPPOSITE AND THEREFORE THE BLOCK DOES NOT MOVE. THE RESULTANT OF THE FORCES ACTING ON THE BODY IS ZERO.
IN A GAME OF TUG OF WAR WHEN BOTH THE TEAMS PULL THE ROPE WITH EQUAL AND OPPOSITE FORCES, THEN THE ROPE REMAINS STATIONARY AS THE FORCES ACTING ON IT ARE EQUAL AND OPPOSITE AND THEIR RESULTANT IS ZERO.
SQUEEZE A RUBBER BALL BETWEEN THE PALMS OF YOUR HANDS. WHAT DO YOU OBSERVE? THE SHAPE OF THE RUBBER BALL CHANGES. THE FORCES APPLIED ON THE BALL ARE EQUAL AND OPPOSITE AND THE RESULTANT OF THESE FORCES DOES NOT MOVE THE OBJECT, INSTEAD THE OBJECT GETS DEFORMED AS LONG AS THE FORCE IS APPLIED. THIS IS A TEMPORARY DEFORMATION.
REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO
Do you want to learn more?
http://www.tutorvista.com/content/science/science-i/force-laws-motion/force-laws-motionindex.php
http://www.physicsclassroom.com/
sábado, 15 de octubre de 2011
06 DESCRIBING MOTION WITH GRAPHS
SEPyC Expected learning:
Elabora e interpreta tablas de datos y gráficas de velocidad-tiempo y aceleración- tiempo para describir y predecir características de diferentes movimientos, a partir de datos que obtiene en experimentos y/o situaciones del entorno.
CLASS 01
The Meaning of Shape for a position - time Graph (Also called distance vs time graphs)
"As the slope goes, so goes the velocity."
The shapes of the position versus time graphs for these two basic types of motion - constant velocity motion and accelerated motion (i.e., changing velocity) - reveal an important principle.
The slope of the line on a position-time graph reveals useful information about the velocity of the object.
Whatever characteristics the velocity has, the slope will exhibit the same (and vice versa):
*If the velocity is constant, then the slope is constant (i.e., a straight line).
*If the velocity is changing, then the slope is changing (i.e., a curved line).
*If the velocity is positive, then the slope is positive (i.e., moving upwards and to the right).
*If the velocity is negative, then the slope is negative (i.e., moving downwards and to the right).
Slope = Velocity
The principle of slope is an incredibly useful principle for extracting relevant information about the motion of objects as described by their position vs. time graph. Once you've practiced the principle a few times, it becomes a very natural means of analyzing position-time graphs.
Remember that...
The slope of a position vs. time graph reveals pertinent information about an object's velocity.
For example,
A small slope means a small velocity;
A negative slope means a negative velocity;
A constant slope (straight line) = a constant velocity;
A changing slope (curved line) = a changing velocity.
Thus the shape of the line on the graph (straight, curving, steeply sloped, mildly sloped, etc.) is descriptive of the object's motion
CLASS 02 Determining the Slope on a position - time Graph
The slope equation says that the slope of a line is found by determining the amount of rise of the line between any two points divided by the amount of run of the line between the same two points. In other words,
1. Pick two points on the line and determine their coordinates.
2. Determine the difference in y-coordinates of these two points (rise).
3. Determine the difference in x-coordinates for these two points (run).
4. Divide the difference in y-coordinates by the difference in x-coordinates (rise/run or slope).
EXAMPLE 1: Consider the graph below. Note that the slope is not positive but rather negative; that is, the line slopes in the downward direction.
Note also that the line on the graph does not pass through the origin. Slope calculations are relatively easy when the line passes through the origin since one of the points is (0,0).
Answer: Slope = -3.0 m/s
Using the two given data points, the rise can be calculated as -24.0 m (the - sign indicates a drop).
The run can be calculated as 8.0 seconds. Thus, the slope is -3.0 m/s.
CLASS 03 Velocity vs. Time Graphs
The slope of a velocity vs time graph represents the acceleration of the object.
Answers: a, d and h apply.
a) TRUE since the line is in the positive region of the graph.
b) FALSE since there is an acceleration (i.e., a changing velocity).
c) FALSE since a negative velocity would be a line in the negative region (i.e., below the horizontal axis).
d) TRUE since the line is approaching the 0-velocity level (the x-axis).
e) FALSE since the line never crosses the axis.
f) FALSE since the line is not moving away from x-axis.
g) FALSE since the line has a negative or downward slope.
h) TRUE since the line is straight (i.e, has a constant slope).
CLASS 04 Relating the Graph Shape to the Object’s Motion
REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO
REVIEW. Check Your Understanding (Repaso).
Describe the motion depicted by the following velocity-time graphs.
In your descriptions, make reference to the direction of motion (+ or - direction), the velocity and acceleration and any changes in speed (speeding up or slowing down) during the various time intervals (e.g., intervals A, B, and C).
Do you want to learn more?
Lessons
http://www.physicsclassroom.com/Class/1DKin/U1L3a.cfm
Videos
http://www.physicsclassroom.com/mmedia/index.cfm#kinema
Elabora e interpreta tablas de datos y gráficas de velocidad-tiempo y aceleración- tiempo para describir y predecir características de diferentes movimientos, a partir de datos que obtiene en experimentos y/o situaciones del entorno.
CLASS 01
The Meaning of Shape for a position - time Graph (Also called distance vs time graphs)
"As the slope goes, so goes the velocity."
The shapes of the position versus time graphs for these two basic types of motion - constant velocity motion and accelerated motion (i.e., changing velocity) - reveal an important principle.
The slope of the line on a position-time graph reveals useful information about the velocity of the object.
Whatever characteristics the velocity has, the slope will exhibit the same (and vice versa):
*If the velocity is constant, then the slope is constant (i.e., a straight line).
*If the velocity is changing, then the slope is changing (i.e., a curved line).
*If the velocity is positive, then the slope is positive (i.e., moving upwards and to the right).
*If the velocity is negative, then the slope is negative (i.e., moving downwards and to the right).
Slope = Velocity
The principle of slope is an incredibly useful principle for extracting relevant information about the motion of objects as described by their position vs. time graph. Once you've practiced the principle a few times, it becomes a very natural means of analyzing position-time graphs.
Remember that...
The slope of a position vs. time graph reveals pertinent information about an object's velocity.
For example,
A small slope means a small velocity;
A negative slope means a negative velocity;
A constant slope (straight line) = a constant velocity;
A changing slope (curved line) = a changing velocity.
Thus the shape of the line on the graph (straight, curving, steeply sloped, mildly sloped, etc.) is descriptive of the object's motion
CLASS 02 Determining the Slope on a position - time Graph
The slope equation says that the slope of a line is found by determining the amount of rise of the line between any two points divided by the amount of run of the line between the same two points. In other words,
1. Pick two points on the line and determine their coordinates.
2. Determine the difference in y-coordinates of these two points (rise).
3. Determine the difference in x-coordinates for these two points (run).
4. Divide the difference in y-coordinates by the difference in x-coordinates (rise/run or slope).
EXAMPLE 1: Consider the graph below. Note that the slope is not positive but rather negative; that is, the line slopes in the downward direction.
Note also that the line on the graph does not pass through the origin. Slope calculations are relatively easy when the line passes through the origin since one of the points is (0,0).
Answer: Slope = -3.0 m/s
Using the two given data points, the rise can be calculated as -24.0 m (the - sign indicates a drop).
The run can be calculated as 8.0 seconds. Thus, the slope is -3.0 m/s.
CLASS 03 Velocity vs. Time Graphs
The slope of a velocity vs time graph represents the acceleration of the object.
Answers: a, d and h apply.
a) TRUE since the line is in the positive region of the graph.
b) FALSE since there is an acceleration (i.e., a changing velocity).
c) FALSE since a negative velocity would be a line in the negative region (i.e., below the horizontal axis).
d) TRUE since the line is approaching the 0-velocity level (the x-axis).
e) FALSE since the line never crosses the axis.
f) FALSE since the line is not moving away from x-axis.
g) FALSE since the line has a negative or downward slope.
h) TRUE since the line is straight (i.e, has a constant slope).
CLASS 04 Relating the Graph Shape to the Object’s Motion
REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO REPASO
REVIEW. Check Your Understanding (Repaso).
Describe the motion depicted by the following velocity-time graphs.
In your descriptions, make reference to the direction of motion (+ or - direction), the velocity and acceleration and any changes in speed (speeding up or slowing down) during the various time intervals (e.g., intervals A, B, and C).
Do you want to learn more?
Lessons
http://www.physicsclassroom.com/Class/1DKin/U1L3a.cfm
Videos
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martes, 4 de octubre de 2011
PREPARE FOR QUIZ (MONDAY OCT /10/ 2011)
Instructions: Answer the 20 questions in English to get the pass for your quiz and get a very useful one extra point for that quiz.
ANSWER & STUDY PAGES 16-22, 57 (IN YOUR PHYSICS BOOK)
Cuestionario sobre ondas en Español
1.¿Qué es una onda?
2.¿Qué es el movimiento ondulatorio?
3.Mencione ejemplos de ondas longitudinales y transversales.
4.¿Cuál es la diferencia entre una onda longitudinal y una transversal?
5.¿Cuáles son las cuatro propiedades básicas de una onda?
6.¿Qué propiedades de las ondas son distancias? ¿Cuáles son medidas relacionadas con el tiempo?
7.¿Cuál es la fórmula que relaciona velocidad, longitud de onda y frecuencia?
8.¿Qué propiedad está directamente relacionada con la energía?
9.Dos ondas tienen la misma longitud de onda y diferente frecuencia. ¿Cómo se comparan sus velocidades?
10.¿Cuál es la diferencia entre las ondas mecánicas y las ondas electromagnéticas?
Questionnaire of waves
1.What is a wave?
2.What is wavelike motion?
3.Give two examples of longitudinal waves and two examples of transversal waves.
4.What is the difference between a longitudinal and a transverse wave?
5.What are the four basic characteristics of a wave?
6.Which of the characteristics are distances? What characteristics are related with time?
7.What is the formula that relates velocity, wavelength and frequency?
8.What is the wave characteristic directly related with energy?
9.Two waves have the same wavelength but different frequency. How can we compare their velocities?
10.What is the difference between mechanical waves and electromagnetic waves?
Cuestionario sobre caída libre en Español
1.¿Qué es la caída libre?
2.¿Cómo es el movimiento de los cuerpos que caen en caída libre?
3.¿Los objetos pesados caen más rápido que los ligeros? ¿Por qué?
4.¿Cuáles fueron los logros de Galileo que lo convirtieron en una de las figuras más importantes de la ciencia?
5.¿Cómo explicó Galileo Galilei la caída de los cuerpos?
6.¿Qué objeto llega primero al suelo, un kilogramo de hierro o dos kiLogramos del mismo material?
7.¿Desde qué altura es más peligroso lanzar una moneda, desde un edificio de 3 pisos o desde un edificio de 30 pisos? ¿Por qué?
8.¿Cuál es el valor de la aceleración de la gravedad? ¿Qué significado práctico tiene ese valor?
9.¿Cuál es la velocidad de un cuerpo de 5 Kg. en caída libre después de 1 segundo? ¿de 3 segundos?, ¿y después de 9 segundos?
10.¿Puede un objeto que se mueve siempre con una rapidez de 50 km/h tener un movimiento acelerado? Explica tu respuesta.
Questionnaire of Free Fall.
1.What is free fall?
2.How is the motion of free falling objects?
3.Heavier objects fall faster than lighter objects? Why?
4.What are Galileo´s achievements that became him in a very important scientist?
5.How did Galileo explain Free Fall?
6.What object touches first the floor, one or two kilograms of iron?
7.What is more dangerous, dropping a coin from a 3-floor building or from a 30-floor building?
8.What is the value of gravity acceleration? What does that mean?
9.What is the velocity of a body in free fall after 1, 2, 3, 4, etc. seconds?
10.Can an object that always moves with a speed of 50 km/hr being accelerating? Explain your answer.
ANSWER & STUDY PAGES 16-22, 57 (IN YOUR PHYSICS BOOK)
Cuestionario sobre ondas en Español
1.¿Qué es una onda?
2.¿Qué es el movimiento ondulatorio?
3.Mencione ejemplos de ondas longitudinales y transversales.
4.¿Cuál es la diferencia entre una onda longitudinal y una transversal?
5.¿Cuáles son las cuatro propiedades básicas de una onda?
6.¿Qué propiedades de las ondas son distancias? ¿Cuáles son medidas relacionadas con el tiempo?
7.¿Cuál es la fórmula que relaciona velocidad, longitud de onda y frecuencia?
8.¿Qué propiedad está directamente relacionada con la energía?
9.Dos ondas tienen la misma longitud de onda y diferente frecuencia. ¿Cómo se comparan sus velocidades?
10.¿Cuál es la diferencia entre las ondas mecánicas y las ondas electromagnéticas?
Questionnaire of waves
1.What is a wave?
2.What is wavelike motion?
3.Give two examples of longitudinal waves and two examples of transversal waves.
4.What is the difference between a longitudinal and a transverse wave?
5.What are the four basic characteristics of a wave?
6.Which of the characteristics are distances? What characteristics are related with time?
7.What is the formula that relates velocity, wavelength and frequency?
8.What is the wave characteristic directly related with energy?
9.Two waves have the same wavelength but different frequency. How can we compare their velocities?
10.What is the difference between mechanical waves and electromagnetic waves?
Cuestionario sobre caída libre en Español
1.¿Qué es la caída libre?
2.¿Cómo es el movimiento de los cuerpos que caen en caída libre?
3.¿Los objetos pesados caen más rápido que los ligeros? ¿Por qué?
4.¿Cuáles fueron los logros de Galileo que lo convirtieron en una de las figuras más importantes de la ciencia?
5.¿Cómo explicó Galileo Galilei la caída de los cuerpos?
6.¿Qué objeto llega primero al suelo, un kilogramo de hierro o dos kiLogramos del mismo material?
7.¿Desde qué altura es más peligroso lanzar una moneda, desde un edificio de 3 pisos o desde un edificio de 30 pisos? ¿Por qué?
8.¿Cuál es el valor de la aceleración de la gravedad? ¿Qué significado práctico tiene ese valor?
9.¿Cuál es la velocidad de un cuerpo de 5 Kg. en caída libre después de 1 segundo? ¿de 3 segundos?, ¿y después de 9 segundos?
10.¿Puede un objeto que se mueve siempre con una rapidez de 50 km/h tener un movimiento acelerado? Explica tu respuesta.
Questionnaire of Free Fall.
1.What is free fall?
2.How is the motion of free falling objects?
3.Heavier objects fall faster than lighter objects? Why?
4.What are Galileo´s achievements that became him in a very important scientist?
5.How did Galileo explain Free Fall?
6.What object touches first the floor, one or two kilograms of iron?
7.What is more dangerous, dropping a coin from a 3-floor building or from a 30-floor building?
8.What is the value of gravity acceleration? What does that mean?
9.What is the velocity of a body in free fall after 1, 2, 3, 4, etc. seconds?
10.Can an object that always moves with a speed of 50 km/hr being accelerating? Explain your answer.
lunes, 3 de octubre de 2011
05 Free Fall
HOW DO OBJECTS FALL?
OBJECTIVE:
1. Study the concept of acceleration as the change of velocity.
2. Analyze the effect of object's weight on free fall.
3. Value the importance of experimentation to get valid conclusions.
I. Introduction to Free Fall
A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall. There are two important motion characteristics that are true of free-falling objects:
• Free-falling objects do not encounter air resistance.
• All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s or 9.8 m/s^2 (often approximated as 10 m/s/s for back-of-the-envelope calculations)
The fact that the distance that the object travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward.
If an object travels downward and speeds up, then its acceleration is downward
GALILEO VS ARISTOTLE
The Acceleration of Gravity
It was learned in the previous part of this lesson that a free-falling object is an object that is falling under the sole influence of gravity. A free-falling object has an acceleration of 9.8 m/s/s, downward (on Earth). This numerical value for the acceleration of a free-falling object is such an important value that it is given a special name. It is known as the acceleration of gravity - the acceleration for any object moving under the sole influence of gravity. A matter of fact, this quantity known as the acceleration of gravity is such an important quantity that physicists have a special symbol to denote it - the symbol g. The numerical value for the acceleration of gravity is most accurately known as 9.8 m/s/s. There are slight variations in this numerical value (to the second decimal place) that are dependent primarily upon on altitude. We will occasionally use the approximated value of 10 m/s/s in The Physics Classroom Tutorial in order to reduce the complexity of the many mathematical tasks that we will perform with this number. By so doing, we will be able to better focus on the conceptual nature of physics without too much of a sacrifice in numerical accuracy.
g = 9.8 m/s/s, downward
( ~ 10 m/s/s, downward)
The value of the acceleration of gravity (g) is different in different gravitational environments (different planets).
If the velocity and time for a free-falling object being dropped from a position of rest were tabulated, then one would note the following pattern
A position versus time graph for a free-falling object is shown below.
Observe that the line on the graph curves. A curved line on a position versus time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration (g = 9.8 m/s/s), it would be expected that its position-time graph would be curved. A further look at the position-time graph reveals that the object starts with a small velocity (slow) and finishes with a large velocity (fast). Since the slope of any position vs. time graph is the velocity of the object, the small initial slope indicates a small initial velocity and the large final slope indicates a large final velocity. Finally, the negative slope of the line indicates a negative (i.e., downward) velocity.
A velocity versus time graph for a free-falling object is shown below.
Observe that the line on the graph is a straight, diagonal line. As learned earlier, a diagonal line on a velocity versus time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration (g = 9,8 m/s/s, downward), it would be expected that its velocity-time graph would be diagonal. A further look at the velocity-time graph reveals that the object starts with a zero velocity (as read from the graph) and finishes with a large, negative velocity; that is, the object is moving in the negative direction and speeding up. An object that is moving in the negative direction and speeding up is said to have a negative acceleration. Since the slope of any velocity versus time graph is the acceleration of the object, the constant, negative slope indicates a constant, negative acceleration. This analysis of the slope on the graph is consistent with the motion of a free-falling object - an object moving with a constant acceleration of 9.8 m/s/s in the downward direction.
Velocity of free falling objects. How Fast?
Free-falling objects are in a state of acceleration. Specifically, they are accelerating at a rate of 9.8 m/s/s. This is to say that the velocity of a free-falling object is changing by 9.8 m/s every second. If dropped from a position of rest, the object will be traveling 9.8 m/s (approximately 10 m/s) at the end of the first second, 19.6 m/s (approximately 20 m/s) at the end of the second second, 29.4 m/s (approximately 30 m/s) at the end of the third second, etc. Thus, the velocity of a free-falling object that has been dropped from a position of rest is dependent upon the time that it has fallen. The formula for determining the velocity of a falling object after a time of t seconds is
vf = g * t
where g is the acceleration of gravity. The value for g on Earth is 9.8 m/s/s. The above equation can be used to calculate the velocity of the object after any given amount of time when dropped from rest. Example calculations for the velocity of a free-falling object after six and eight seconds are shown below.
Example Calculations:
At t = 6 s vf = (9.8 m/s2) * (6 s) = 58.8 m/s
At t = 8 s vf = (9.8 m/s2) * (8 s) = 78.4 m/s
Distance traveled of free falling objects. How Far?
The distance that a free-falling object has fallen from a position of rest is also dependent upon the time of fall. This distance can be computed by use of a formula; the distance fallen after a time of t seconds is given by the formula.
d = 0.5 * g * t2
where g is the acceleration of gravity (9.8 m/s/s on Earth). Example calculations for the distance fallen by a free-falling object after one and two seconds are shown below.
Example Calculations:
At t = 1 s d = (0.5) * (9.8 m/s2) * (1 s)2 = 4.9 m
At t = 2 s d = (0.5) * (9.8 m/s2) * (2 s)2 = 19.6 m
At t = 5 s d = (0.5) * (9.8 m/s2) * (5 s)2 = 123 m (rounded from 122.5 m)
The diagram below (not drawn to scale) shows the results of several distance calculations for a free-falling object dropped from a position of rest.
The Big Misconception
It was stated that the acceleration of a free-falling object (on earth) is 9.8 m/s/s. This value (known as the acceleration of gravity) is the same for all free-falling objects regardless of how long they have been falling, or whether they were initially dropped from rest or thrown up into the air. Yet the questions are often asked "doesn't a more massive object accelerate at a greater rate than a less massive object?" "Wouldn't an elephant free-fall faster than a mouse?" This question is a reasonable inquiry that is probably based in part upon personal observations made of falling objects in the physical world. After all, nearly everyone has observed the difference in the rate of fall of a single piece of paper (or similar object) and a textbook. The two objects clearly travel to the ground at different rates - with the more massive book falling faster.
The answer to the question (doesn't a more massive object accelerate at a greater rate than a less massive object?) is absolutely not! That is, absolutely not if we are considering the specific type of falling motion known as free-fall. Free-fall is the motion of objects that move under the sole influence of gravity; free-falling objects do not encounter air resistance. More massive objects will only fall faster if there is an appreciable amount of air resistance present.
The actual explanation of why all objects accelerate at the same rate involves the concepts of force and mass. The details will be discussed later. At that time, you will learn that the acceleration of an object is directly proportional to force and inversely proportional to mass. Increasing force tends to increase acceleration while increasing mass tends to decrease acceleration. Thus, the greater force on more massive objects is offset by the inverse influence of greater mass. Subsequently, all objects free fall at the same rate of acceleration, regardless of their mass.
III. ACCELERATION
EXTRA CREDIT
If you want to learn more, visit http://www.physicsclassroom.com/Class/1DKin/U1L5a.cfm
OBJECTIVE:
1. Study the concept of acceleration as the change of velocity.
2. Analyze the effect of object's weight on free fall.
3. Value the importance of experimentation to get valid conclusions.
I. Introduction to Free Fall
A free falling object is an object that is falling under the sole influence of gravity. Any object that is being acted upon only by the force of gravity is said to be in a state of free fall. There are two important motion characteristics that are true of free-falling objects:
• Free-falling objects do not encounter air resistance.
• All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s or 9.8 m/s^2 (often approximated as 10 m/s/s for back-of-the-envelope calculations)
The fact that the distance that the object travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward.
If an object travels downward and speeds up, then its acceleration is downward
GALILEO VS ARISTOTLE
The Acceleration of Gravity
It was learned in the previous part of this lesson that a free-falling object is an object that is falling under the sole influence of gravity. A free-falling object has an acceleration of 9.8 m/s/s, downward (on Earth). This numerical value for the acceleration of a free-falling object is such an important value that it is given a special name. It is known as the acceleration of gravity - the acceleration for any object moving under the sole influence of gravity. A matter of fact, this quantity known as the acceleration of gravity is such an important quantity that physicists have a special symbol to denote it - the symbol g. The numerical value for the acceleration of gravity is most accurately known as 9.8 m/s/s. There are slight variations in this numerical value (to the second decimal place) that are dependent primarily upon on altitude. We will occasionally use the approximated value of 10 m/s/s in The Physics Classroom Tutorial in order to reduce the complexity of the many mathematical tasks that we will perform with this number. By so doing, we will be able to better focus on the conceptual nature of physics without too much of a sacrifice in numerical accuracy.
g = 9.8 m/s/s, downward
( ~ 10 m/s/s, downward)
The value of the acceleration of gravity (g) is different in different gravitational environments (different planets).
If the velocity and time for a free-falling object being dropped from a position of rest were tabulated, then one would note the following pattern
A position versus time graph for a free-falling object is shown below.
Observe that the line on the graph curves. A curved line on a position versus time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration (g = 9.8 m/s/s), it would be expected that its position-time graph would be curved. A further look at the position-time graph reveals that the object starts with a small velocity (slow) and finishes with a large velocity (fast). Since the slope of any position vs. time graph is the velocity of the object, the small initial slope indicates a small initial velocity and the large final slope indicates a large final velocity. Finally, the negative slope of the line indicates a negative (i.e., downward) velocity.
A velocity versus time graph for a free-falling object is shown below.
Observe that the line on the graph is a straight, diagonal line. As learned earlier, a diagonal line on a velocity versus time graph signifies an accelerated motion. Since a free-falling object is undergoing an acceleration (g = 9,8 m/s/s, downward), it would be expected that its velocity-time graph would be diagonal. A further look at the velocity-time graph reveals that the object starts with a zero velocity (as read from the graph) and finishes with a large, negative velocity; that is, the object is moving in the negative direction and speeding up. An object that is moving in the negative direction and speeding up is said to have a negative acceleration. Since the slope of any velocity versus time graph is the acceleration of the object, the constant, negative slope indicates a constant, negative acceleration. This analysis of the slope on the graph is consistent with the motion of a free-falling object - an object moving with a constant acceleration of 9.8 m/s/s in the downward direction.
Velocity of free falling objects. How Fast?
Free-falling objects are in a state of acceleration. Specifically, they are accelerating at a rate of 9.8 m/s/s. This is to say that the velocity of a free-falling object is changing by 9.8 m/s every second. If dropped from a position of rest, the object will be traveling 9.8 m/s (approximately 10 m/s) at the end of the first second, 19.6 m/s (approximately 20 m/s) at the end of the second second, 29.4 m/s (approximately 30 m/s) at the end of the third second, etc. Thus, the velocity of a free-falling object that has been dropped from a position of rest is dependent upon the time that it has fallen. The formula for determining the velocity of a falling object after a time of t seconds is
vf = g * t
where g is the acceleration of gravity. The value for g on Earth is 9.8 m/s/s. The above equation can be used to calculate the velocity of the object after any given amount of time when dropped from rest. Example calculations for the velocity of a free-falling object after six and eight seconds are shown below.
Example Calculations:
At t = 6 s vf = (9.8 m/s2) * (6 s) = 58.8 m/s
At t = 8 s vf = (9.8 m/s2) * (8 s) = 78.4 m/s
Distance traveled of free falling objects. How Far?
The distance that a free-falling object has fallen from a position of rest is also dependent upon the time of fall. This distance can be computed by use of a formula; the distance fallen after a time of t seconds is given by the formula.
d = 0.5 * g * t2
where g is the acceleration of gravity (9.8 m/s/s on Earth). Example calculations for the distance fallen by a free-falling object after one and two seconds are shown below.
Example Calculations:
At t = 1 s d = (0.5) * (9.8 m/s2) * (1 s)2 = 4.9 m
At t = 2 s d = (0.5) * (9.8 m/s2) * (2 s)2 = 19.6 m
At t = 5 s d = (0.5) * (9.8 m/s2) * (5 s)2 = 123 m (rounded from 122.5 m)
The diagram below (not drawn to scale) shows the results of several distance calculations for a free-falling object dropped from a position of rest.
The Big Misconception
It was stated that the acceleration of a free-falling object (on earth) is 9.8 m/s/s. This value (known as the acceleration of gravity) is the same for all free-falling objects regardless of how long they have been falling, or whether they were initially dropped from rest or thrown up into the air. Yet the questions are often asked "doesn't a more massive object accelerate at a greater rate than a less massive object?" "Wouldn't an elephant free-fall faster than a mouse?" This question is a reasonable inquiry that is probably based in part upon personal observations made of falling objects in the physical world. After all, nearly everyone has observed the difference in the rate of fall of a single piece of paper (or similar object) and a textbook. The two objects clearly travel to the ground at different rates - with the more massive book falling faster.
The answer to the question (doesn't a more massive object accelerate at a greater rate than a less massive object?) is absolutely not! That is, absolutely not if we are considering the specific type of falling motion known as free-fall. Free-fall is the motion of objects that move under the sole influence of gravity; free-falling objects do not encounter air resistance. More massive objects will only fall faster if there is an appreciable amount of air resistance present.
The actual explanation of why all objects accelerate at the same rate involves the concepts of force and mass. The details will be discussed later. At that time, you will learn that the acceleration of an object is directly proportional to force and inversely proportional to mass. Increasing force tends to increase acceleration while increasing mass tends to decrease acceleration. Thus, the greater force on more massive objects is offset by the inverse influence of greater mass. Subsequently, all objects free fall at the same rate of acceleration, regardless of their mass.
III. ACCELERATION
EXTRA CREDIT
If you want to learn more, visit http://www.physicsclassroom.com/Class/1DKin/U1L5a.cfm
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