Mechanical Energy

ENERGY AND WORK

Did you put a book in your backpack this morning? If so, the you did work on the book. Recall that work is done when a force moves an object.
Energy is the ability to do work or cause change upon other objects
When you do work on an object, some of your energy is transferred to that object.
You can think of work as the transfer of energy. When energy is transferred, the object upon which the work is done gains energy.
Energy is measured in joules (the same units as work).

What is mechanical energy?

*The energy acquired by the objects upon which work is done is known as mechanical energy.
*Mechanical energy = Potential energy + kinetic energy
*Total mechanical energy is the energy possessed by an object due to either its motion or its stored energy of position

GRAVITATIONAL POTENTIAL ENERGY

*Energy that results from the position (height) or shape (mass) of an object is called potential energy
*Gravitational potential energy depends on the MASS and the HEIGHT
*When you lift a book up to your desk from the floor you transfer energy to it.
*The energy you transfer is stored and it might be used later if the book falls.

Calculating Gravitational potential energy

PEgrav = mass • gravity • height
PEgrav = m *• g • h
PEgrav = (# kg ) * (# m/s/s) * (# m)
In the above equation,
- m represents the mass of the object,
- h represents the height of the object and
- g represents the gravitational field strength (9.8 m/s^2 on Earth) - sometimes referred to as the acceleration of gravity.

We measure PEgrav in Joules

PEgrav = Joules
Like work, the standard metric unit of measurement for potential energy is the Joule.

MOTION-KINETIC ENERGY

The energy an object has due to its motion is called kinetic energy. For example:

*Moving objects, like cars and motorcycles have one type of energy: kinetic energy.
*A moving object can do work when it strikes another object and moves it.
* A swinging hammer does work on a nail as it drives the nail intro the piece of wood.
*The hammer has energy because it can do work.

Factors affecting kinetic energy

SPEED
*The faster an object moves, the more kinetic energy it has. Example: A tennis ball that travels at a much greater speed would hurt more.

MASS
*A ball rolls across the ground and hits you in the foot. (tennis ball vs bowling ball). The bowling ball has more kinetic energy because it has a greater mass.

Calculating kinetic energy

where:
m = mass of object
v = speed of object

This equation reveals that the kinetic energy of an object is directly proportional to the mass and the square of its speed.


Do changes in speed and mass have the same effect on the kinetic energy?
NO
*Changing the speed of the wagon will have a greater effect on its kinetic energy than changing its mass by the same factor.
*Doubling the mass of the wagon will double its kinetic energy.
*Doubling the speed of the wagon will quadruple its kinetic energy.


Kinetic energy is dependent upon the square of the speed.
*For a twofold increase in speed, the kinetic energy will increase by a factor of four.
*For a threefold increase in speed, the kinetic energy will increase by a factor of nine.
*For a fourfold increase in speed, the kinetic energy will increase by a factor of sixteen.

Kinetic Energy = Joules
Like work and potential energy, the standard metric unit of measurement for kinetic energy is the Joule.

Transformations from potential energy to kinetic energy

Rubber band

When you stretch a rubber band, you give it elastic potential energy. If you let it go, the rubber band flies across the room. When the rubber band is moving, it has kinetic energy.
The potential energy of the stretched rubber has transformed to the kinetic energy of the moving rubber band.

A lift motor

When you lift a heavy object against the gravitational field, you exert energy or give the object energy as you lift it. This potential energy later becomes kinetic energy if you let go of the object and it falls. A lift motor provides gravitational potential energy when lifting the car to higher floors. If the cable was cut the potential energy gained by the car would be transferred into kinetic energy as the car fell back towards the Earth, It would have maximum potential energy at the highest floor and maximum kinetic energy when it hit the Earth at the ground floor

Fallling Tennis ball

As the height of the ball decreases, it loses potential energy.
At the same time, its kinetic energy increases because its speed increases.
Its potential energy is transformed into kinetic energy.

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Print this review and solve it this friday 25 inside the classroom.

1. A cart is loaded with a brick and pulled at constant speed along an inclined plane to the height of a seat-top. If the mass of the loaded cart is 3.0 kg and the height of the seat top is 0.45 meters, then what is the potential energy of the loaded cart at the height of the seat-top?

2. Suppose a boy is pulling a 10-kg wagon at a speed if 1 m/s. What is the kinetic energy of the wagon?

3. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s.

4. If the roller coaster car in the above problem were moving with twice the speed, then what would be its new kinetic energy? Show your procedure.

5. A bike rider approaches a hill with a speed of 8.5 m/s. The total mass of the bike and the rider is 85 kg. Find the kinetic energy of the bike and rider.

6. Missy Diwater, the former platform diver for the Ringling Brother's Circus, had a kinetic energy of 12000 J just prior to hitting the bucket of water. If Missy's mass is 40 kg, then what is her speed?

In the following descriptions, the only forces doing work upon the objects are internal forces - gravitational and spring forces.
Thus, energy is transformed from KE to PE (or vice versa) while the total amount of mechanical energy is conserved.
Read each description and indicate whether energy is transformed from KE to PE or from PE to KE.

7. A ball falls from a height of 2 meters in the absence of air resistance.

PE to KE
The ball is losing height (falling) and gaining speed. Thus, the internal or conservative force (gravity) transforms the energy from PE (height) to KE (speed).

8. A skier glides from location A to location B across a friction free ice.

PE to KE
The skier is losing height (the final location is lower than the starting location) and gaining speed (the skier is faster at B than at A). Thus, the internal force or conservative (gravity) transforms the energy from PE (height) to KE (speed).

9. A baseball is traveling upward towards a man in the bleachers.

KE to PE
The ball is gaining height (rising) and losing speed (slowing down). Thus, the internal or conservative force (gravity) transforms the energy from KE (speed) to PE (height).

10. A bungee cord begins to exert an upward force upon a falling bungee jumper.

KE to PE
The jumper is losing speed (slowing down) and the bungee cord is stretching. Thus, the internal or conservative force (spring) transforms the energy from KE (speed) to PE (a stretched "spring"). One might also argue that the gravitational PE is decreasing due to the loss of height.

11. The spring of a dart gun exerts a force on a dart as it is launched from an initial rest position.

PE to KE
The spring changes from a compressed state to a relaxed state and the dart starts moving. Thus, the internal or conservative force (spring) transforms the energy from PE (a compressed spring) to KE (speed).

Find more information at:

http://www.kids.esdb.bg/index.html

http://www.physicsclassroom.com/Class/energy/U5L1b.cfm

EXPERIENCIAS DESENCADENANTES

LAS EXPERIENCIAS DESENCADENANTES

Abriendo ventanas
Las experiencias desencadenantes o estimuladoras tienen como propósito abrir ventanas a las niñas y niños, poniéndolos en contacto con fenómenos, ideas y prácticas poco conocidas por ellos y que encierran carga formativa.
Contribuyen a impregnar a la escuela de realismo, alejándola de artificiosidades.
Además gracias a algunas de ellas los niños no tienen que dejar afuera su vida extra-escolar cuando entran al aula. Al contrario con estas experiencias la escuela da la bienvenida al mundo infantil y lo aprovecha para que, a partir de él, a partir de las realidades que ya les son conocidas, los niños adquieran nuevos saberes y destrezas.
Amplían el acervo de experiencias de los estudiantes, base para mayores reflexiones y estudios: creemos muy importante el papel de alimentadoras de la mente que tienen este tipo de actividades. […] van formando un conjunto de conocimientos, prácticas, vivencias y emociones, que poco a poco se van entretejiendo en la mente de los niños y que dan el fundamento para que surjan nuevas inquietudes…
La colaboración de otras instituciones se hace necesaria para muchas experiencias desencadenantes: la sociedad debe abrirse para facilitar actividades formativas a los niños [...].

Base vivencial para construir conocimiento

Las experiencias desencadenantes forman un sustrato de vivencias directas, observaciones e intercambios sobre los cuales es más fácil y firme la construcción del conocimiento escolar.
Un enfoque que nos parece muy propicio es ofrecer durante los primeros grados abundantes experiencias que permitan ir construyendo intuiciones poderosas, que puedan luego trabajarse explícita y sistemáticamente.
Son muy importantes las experiencias que contradicen la vivencia cotidiana, por ejemplo, las de movimiento con roce mínimo, caída de cuerpos en el vacío, o comportamiento de gases a muy bajas temperaturas. Ellas permiten el acceso a realidades ocultas por las condiciones usuales de nuestra vida.
Las exploraciones y observaciones, tanto bajo la forma de experiencias desencadenantes como bajo la más modesta de actividades cortas y fértiles, deben ser diversas y abundantes, y deben sucederse año tras año, en diferentes contextos. Ellas proveen imágenes y episodios que pueden recordarse y reelaborarse posteriormente.
Son actividades exploratorias antes que conclusivas.

Visitas

Las visitas pueden ser de toda clase, de un equipo o de un solo alumno, según el caso. Pueden darse algunas más abiertas, menos preparadas por los niños […]. Y también son convenientes las visitas que ocurren dentro de proyectos de investigación […]. Combinar ambos tipos de visitas es importante, pues si todas las salidas fueran exploratorias quizás el aprendizaje sería demasiado superficial. Y si todas las visitas fueran investigativas posiblemente los niños se verían demasiado presionados por las exigencias de la labor y podrían perder aprecio y disfrute por salidas y excursiones que conllevaran siempre tanta demanda de trabajo previo y posterior.
Las salidas abren también nuevas oportunidades para la integración del grupo y su mejor relación con el educador […] y ofrecen momentos de interacción social más allá de los tradicionalmente pautados…

Conversaciones con expertos

Se invita a la clase o se va a visitar a una persona con quien vale la pena hablar, pues tiene conocimientos, experiencias y/o destrezas que puede comunicarnos.
El experto aporta conocimientos abundantes, actualizados y directos sobre su área, complementando la acción del educador.
Además el experto puede incidir de manera interesante en el área afectiva: por el interés por su campo que transmite, por los valores que defiende, por la emoción de los relatos de sus vivencias, etcétera.
La gama de expertos puede ser muy amplia: desde un escalador de montañas hasta una especialista en educación sexual, desde una pintora hasta un ebanista, desde una entomóloga hasta un anciano de la comunidad.
El contacto con científicos y tecnólogos y con trabajadores especializados en áreas científicas y tecnológicas es además interesante para el estímulo de vocaciones en tales campos.

Instrumentos que abren mundos

Pensamos en un primer encuentro estimulador, donde la idea será familiarizarse con el aparato y asomarse al mundo que el mismo abre.
Ejemplos de este tipo de instrumentos serían la lupa binocular, el microscopio, el telescopio, la radio de onda corta, la red de redes telemática o el correo electrónico.

Conferencias de los niños

La técnica de las conferencias, desarrollada por la escuela freinetiana, consiste en que siempre que un niño tenga un tema interesante que presentar a sus compañeros puede anotarse para hacerlo. Realizará así una pequeña exposición, mostrará fotografías y objetos, quizás hará escuchar parte de un disco y, de acuerdo a su edad, se apoyará en algunas transparencias o podrá utilizar mapas o gráficos. Los temas de las conferencias no deben ser impuestos por el maestro, sino que han de ser asuntos conocidos por los niños y sobre los cuales ellos quieren hablar…

Exhibiciones

Montadas por el docente o por un equipo de niños: se centran en algún tema interesante y recogen muestras […] e incluso materiales y equipos para que el público realice observaciones o pequeñas experiencias […]. Las exhibiciones son seguramente un proyecto para quienes las monta, pero una experiencia desencadenante para quienes las visitan.

El cultivo de plantas

Se trata de una experiencia amplia, a mediano plazo, que permite aprendizajes muy diversos. Puede plantearse bajo la modalidad de huerto escolar, jardín de flores, jardín o jardinera de plantas aromáticas, siembra en macetas, acuario de algas y/o plantas superiores, entre otras opciones.

Contactos con animales

[…] creemos que el contacto más o menos cercano con animales diversos es una experiencia enriquecedora, que puede plantear interrogantes para el estudio científico. Invertebrados y algunos vertebrados pequeños pueden mantenerse en el aula por algunos días, otros animales pueden entrar en ella por una jornada, y aun a otros podemos visitarlos en su propio ambiente natural.

La cocina

Cocinar en la escuela es una actividad anchurosa, que alude de alguna manera a diversos temas científicos: mezclas y soluciones, coloides, cambios químicos, combustión, calor, mediciones de peso, volumen y tiempo, percepción de olores y sabores... También afecta a la educación para la salud, en el aprendizaje por la práctica de hábitos higiénicos o en la consideración de diversos tipos de alimentos y sus propiedades y efectos.
Rica a la vez en componentes sensoriales y estéticos.

El barro

Trabajar el barro es una actividad bastante abierta, de la cual pueden surgir distintos interrogantes y nuevas actividades y proyectos. Esta labor plantea retos en cuanto a tipos de barro utilizado, mezclas, moldes, uso del torno, energía solar, resistencia de materiales y de formas diversas…

Proyectos exploratorios

Son trabajos que invitan a explorar libremente en un área, a «jugar» con materiales y equipos sin muchas directrices.
Serían ejemplos de proyectos exploratorios: interaccionar con imanes y materiales metálicos y no metálicos; intentar mezclas entre líquidos y sólidos diversos; indagar lo que pasa con poleas y pesos variados... Luego de estos encuentros de familiarización y exploración pueden darse discusiones, lecturas, exposiciones del docente, observación de videos…

Acción comunitaria

Participación de los niños o jóvenes en alguna acción de tipo comunitario, organizada por la propia escuela o, más comúnmente, por otra institución social. Algunas acciones pueden ser de una sola jornada, como siembra de arbolitos, recogida de basuras el Día de las playas, entrega de propaganda a la puerta de la escuela en el Día de No Fumar, etcétera.

Texto libre

Son escritos que los niños traen a la escuela cuando así lo desean. Pueden ser relatos de cosas que les han pasado o han presenciado, cuentos o poesías inventados por ellos, opiniones, propuestas...
Es importante el trabajo que se hace con los textos: cada niña o niño lee el suyo, o bien el maestro lo hace. Recuérdese que nunca habrá treinta textos el mismo día, pues no es una tarea sino un aporte espontáneo: podrá haber cinco, uno o ninguno. Luego, la clase elige uno a unos pocos que consideran más interesantes. Puede ser que se le pida a la autora o autor que lo complete o lo mejore de alguna manera, añadiendo precisiones o aclarando ideas.
En ocasiones, con textos libres sobre un mismo tema pueden hacerse monografías (de animales, de ambientes, de problemas de salud...). En todo caso, los textos no usados de otra manera o bien las copias de los que tienen otros destinos pasan al portafolio de cada niño.
Esta actividad permite mejorar el dominio de la escritura y la lectura. Y afina las capacidades de observación, descripción y narración.
La misma formación científica lograda en la escuela podrá enriquecer los textos libres, pues los niños manejarán conceptos más variados y potentes y, al saber más, podrán observar mejor su entorno.

Dibujo libre

Es una técnica similar a la anteriormente descrita, pero basada en ilustraciones. En ocasiones puede primar en ella lo artístico, en otras lo informativo o lo testimonial. Los dibujos también pueden evaluarse colectivamente, como los textos. Recordemos no alterar su carácter libre, pues de lo contrario se desvirtúa la actividad.

Los niños plantean sus propias preguntas

Durante el desarrollo de algunos temas especialmente propicios, se tiene una hoja grande pegada en la cartelera o en la pared para que los niños que quieran vayan anotando sus preguntas, firmadas. Luego de un tiempo, se analiza la lista de interrogantes: ¿qué preguntas se pueden responder entre todos?, ¿qué preguntas quisieran consultar en la biblioteca?, ¿qué preguntas quedan pendientes para grados superiores? Hay incluso preguntas que los científicos todavía están estudiando y que no tienen aún respuesta fundada.

Lecturas «libres» y del docente

La propuesta es leerlas a los niños poesías, fábulas, cuentos sobre temas vinculados a la clase de ciencias, porque aludan a animales, plantas, diversos ambientes, el agua, los fenómenos del tiempo, profesiones determinadas... También, leerles libros informativos interesantes, o capítulos de los mismos: animales de la selva, vida en una estación espacial, bibliografía de un científico o tecnólogo, episodios llamativos de la historia de la ciencia o de la tecnología... De estos textos pueden leerse unas pocas páginas cada día, para no cansar a los estudiantes.

Canciones

Cantar canciones relacionadas con ambientes naturales, animales, plantas, oficios, alimentos... Importa cuidar la calidad artística de las canciones elegidas, así como la de los cuentos y poesías...
Conviene buscar canciones en los repertorios infantiles y folklóricos (tanto propios como de otros países), así como en los de compositores populares y más «académicos».

Colecciones de obras de arte

La idea es coleccionar reproducciones de pinturas, dibujos y grabados sobre temas de la naturaleza: mar, árboles, flores, perros, caballos, selva, sabana... Conviene buscar autores nacionales y de otros países.

Videos

Observar películas de ficción o documentales que puedan tener algún interés para el área. Por una parte, documentales sobre ecosistemas diversos, viajes de exploración, vidas de científicos y tecnólogos, entre otros. Puede irse organizando una buena videoteca gracias a grabaciones de programas relevantes de televisión, a donaciones de empresas y a algunas compras. En ocasiones, luego de la proyección puede organizarse un cine-foro.

Correspondencia interescolar

Anima a los niños a leer y a escribir, puesto que se hace con un sentido: para comunicarse con otros niños.
Los alumnos no solamente pueden intercambiarse escritos, sino también dibujos, fotografías (incluso de ellos mismos trabajando en clase o en salidas), casetes grabados por ellos mismos, y hasta objetos como minerales, flores, dulces típicos o pequeñas artesanías.
El intercambio epistolar vale más la pena cuando se desarrolla entre escuelas de localidades diferentes, preferiblemente situadas en zonas disímiles (costa y montaña, campo y metrópolis, indígenas y criollos), lo que asegura que los niños tendrán novedades que comunicarse entre sí.

Energy

Visit the next pages to get more information:

http://www.physicsclassroom.com/Class/energy/
http://38.96.246.204/kids/


WORK = Force x Displacement

When a force acts upon an object to cause a displacement of the object, it is said that work was done upon the object. There are three key ingredients to work - force, displacement, and cause. In order for a force to qualify as having done work on an object, there must be a displacement and the force must cause the displacement. There are several good examples of work that can be observed in everyday life - a horse pulling a plow through the field, a father pushing a grocery cart down the aisle of a grocery store, a freshman lifting a backpack full of books upon her shoulder, a weightlifter lifting a barbell above his head, an Olympian launching the shot-put, etc. In each case described here there is a force exerted upon an object to cause that object to be displaced.

Examples:

1. A teacher applies a force to a wall and becomes exhausted.
No. This is not an example of work. The wall is not displaced. A force must cause a displacement in order for work to be done.

2. A book falls off a table and free falls to the ground.
Yes. This is an example of work. There is a force (gravity) which acts on the book which causes it to be displaced in a downward direction (i.e., "fall").

3. A rocket accelerates through space.
Yes. This is an example of work. There is a force (the expelled gases push on the rocket) which causes the rocket to be displaced through space.

4. A waiter carries a tray full of meals above his head by one arm straight across the room at constant speed.
No. This is not an example of work. There is a force (the waiter pushes up on the tray) and there is a displacement (the tray is moved horizontally across the room). Yet the force does not cause the displacement. To cause a displacement, there must be a component of force in the direction of the displacement.

Units of Work

Whenever a new quantity is introduced in physics, the standard metric units associated with that quantity are discussed. In the case of work (and also energy), the standard metric unit is the Joule (abbreviated J). One Joule is equivalent to one Newton of force causing a displacement of one meter. In other words,

The Joule is the unit of work.
1 Joule = 1 Newton * 1 meter
1 J = 1 N * m


ENERGY

Mechanical Energy is the Ability to Do Work

An object that possesses mechanical energy is able to do work. In fact, mechanical energy is often defined as the ability to do work. Any object that possesses mechanical energy - whether it is in the form of potential energy or kinetic energy - is able to do work. That is, its mechanical energy enables that object to apply a force to another object in order to cause it to be displaced.

What Is Energy?
Energy makes change possible. We use it to do things for us. It moves cars along the road and boats over the water. It bakes a cake in the oven and keeps ice frozen in the freezer. It plays our favorite songs on the radio and lights our homes. Energy is needed for our bodies to grow and it allows our minds to think.

Scientists define energy as the ability to do work. Modern civilization is possible because we have learned how to change energy from one form to another and use it to do work for us and to live more comfortably.

Examples:

1. A classic example involves the massive wrecking ball of a demolition machine. The wrecking ball is a massive object that is swung backwards to a high position and allowed to swing forward into building structure or other object in order to demolish it. Upon hitting the structure, the wrecking ball applies a force to it in order to cause the wall of the structure to be displaced. The diagram below depicts the process by which the mechanical energy of a wrecking ball can be used to do work.

2. A hammer is a tool that utilizes mechanical energy to do work. The mechanical energy of a hammer gives the hammer its ability to apply a force to a nail in order to cause it to be displaced. Because the hammer has mechanical energy (in the form of kinetic energy), it is able to do work on the nail. Mechanical energy is the ability to do work.

3. Another example that illustrates how mechanical energy is the ability of an object to do work can be seen any evening at your local bowling alley. The mechanical energy of a bowling ball gives the ball the ability to apply a force to a bowling pin in order to cause it to be displaced. Because the massive ball has mechanical energy (in the form of kinetic energy), it is able to do work on the pin. Mechanical energy is the ability to do work.

4. A dart gun is still another example of how mechanical energy of an object can do work on another object. When a dart gun is loaded and the springs are compressed, it possesses mechanical energy. The mechanical energy of the compressed springs gives the springs the ability to apply a force to the dart in order to cause it to be displaced. Because of the springs have mechanical energy (in the form of elastic potential energy), it is able to do work on the dart. Mechanical energy is the ability to do work.

5. A common scene in some parts of the countryside is a "wind farm." High-speed winds are used to do work on the blades of a turbine at the so-called wind farm. The mechanical energy of the moving air gives the air particles the ability to apply a force and cause a displacement of the blades. As the blades spin, their energy is subsequently converted into electrical energy (a non-mechanical form of energy) and supplied to homes and industries in order to run electrical appliances. Because the moving wind has mechanical energy (in the form of kinetic energy), it is able to do work on the blades. Once more, mechanical energy is the ability to do work.

FORMS OF ENERGY

Energy forms are either potential or kinetic. Potential energy comes in forms that are stored including — chemical, gravitational, elastic, and nuclear. Kinetic energy forms are doing work — like electrical, heat, light, motion, and sound.

Potential Energy

An object can store energy as the result of its position. For example, the heavy ball of a demolition machine is storing energy when it is held at an elevated position. This stored energy of position is referred to as potential energy. Similarly, a drawn bow is able to store energy as the result of its position. When assuming its usual position (i.e., when not drawn), there is no energy stored in the bow. Yet when its position is altered from its usual equilibrium position, the bow is able to store energy by virtue of its position. This stored energy of position is referred to as potential energy. Potential energy is the stored energy of position possessed by an object.

Kinetic Energy
Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another). To keep matters simple, we will focus upon translational kinetic energy

THERE ARE NINE, NUEVE (9) TYPES OF ENERGY. MAKE A DRAWING FOR EACH ONE

I. POTENTIAL ENERGY

1. Chemical Energy is energy stored in the bonds of atoms and molecules. Batteries, biomass, petroleum, natural gas, and coal are examples of stored chemical energy. Chemical energy is converted to thermal energy when we burn wood in a fireplace or burn gasoline in a car's engine.

2. Elastic Energy stored in objects by tension. Compressed springs and stretched rubber bands are examples of stored mechanical energy.

3. Nuclear Energy is energy stored in the nucleus of an atom — the energy that holds the nucleus together. Very large amounts of energy can be released when the nuclei are combined or split apart. Nuclear power plants split the nuclei of uranium atoms in a process called fission. The sun combines the nuclei of hydrogen atoms in a process called fusion.

4. Gravitational Energy is energy stored in an object's height. The higher and heavier the object, the more gravitational energy is stored. When you ride a bicycle down a steep hill and pick up speed, the gravitational energy is being converted to motion energy. Hydropower is another example of gravitational energy, where the dam "piles" up water from a river into a reservoir

II. KINETIC ENERGY

5. Radiant Energy is electromagnetic energy that travels in transverse waves. Radiant energy includes visible light, x-rays, gamma rays and radio waves. Light is one type of radiant energy. Sunshine is radiant energy, which provides the fuel and warmth that make life on Earth possible.

6. Thermal Energy, or heat, is the vibration and movement of the atoms and molecules within substances. As an object is heated up, its atoms and molecules move and collide faster. Geothermal energy is the thermal energy in the Earth.

7. Motion Energy is energy stored in the movement of objects. The faster they move, the more energy is stored. It takes energy to get an object moving, and energy is released when an object slows down. Wind is an example of motion energy. A dramatic example of motion is a car crash, when the car comes to a total stop and releases all its motion energy at once in an uncontrolled instant.

8. Sound is the movement of energy through substances in longitudinal (compression/rarefaction) waves. Sound is produced when a force causes an object or substance to vibrate — the energy is transferred through the substance in a wave. Typically, the energy in sound is far less than other forms of energy.

9. Electrical Energy is delivered by tiny charged particles called electrons, typically moving through a wire. Lightning is an example of electrical energy in nature, so powerful that it is not confined to a wire.

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FOR FRIDAY NOVEMBER 18TH 2011

1. What is work? Give 3 examples.
2. What is energy? Give 3 examples.
3. What are the two basic types of energy?
4. What is kinetic energy? Give 3 examples.
5. What is potential energy? Give 3 examples
6. What is the difference between elastic potential energy and gravitational potential energy?
7. When you stretch a rubber band, you give it
A) Kinetic energy
B) Electrical energy
C) Potential Energy
D) Chemical energy
8.What is the energy stored in the nucleus of an atom called?
A) Electrical energy B) Chemical energy
C) Thermal energy D) Nuclear energy
9.When you heat a pot of water over a flame, what form of energy is added to the water?
10. Why does wind have energy?
A) It can change direction B) It can do work
C) It moves through space as waves D) It is electrically charged.
11. What is the SI used to express gravitational potential energy?
A) Newton B) kilowatt C) Horsepower D) Joule
12. Which energy transformation takes place when wood is burned?
A) Nuclear energy is transformed to thermal energy
B) Thermal energy is transformed to electrical energy
C) Chemical energy is transformed to thermal energy
D) Mechanical energy is transformed to thermal energy.
13. Classify the next forms of energy from the weakest to the strongest.
Gravitational potential energy
Motion energy
Sound energy
Nuclear energy
Thermal energy
Elastic potential energy
Electrical energy
Electromagnetic (Radiant) energy
Chemical energy

Review Newton's Laws (Answers)

1. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. The rock will
a. gradually stop.
b. continue in motion in the same direction at constant speed.
According to Newton's first law, the rock will continue in motion in the same direction at constant speed.
2. A 2-kg object is moving horizontally with a speed of 4 m/s. How much net force is required to keep the object moving at this speed and in this direction? Answer: 0 N
An object in motion will maintain its state of motion. The presence of an unbalanced force changes the velocity of the object.
3. Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why.
Tosh is correct. Inertia is that quantity which depends solely upon mass. The more mass, the more inertia. Momentum is another quantity in Physics which depends on both mass and speed. Momentum will be discussed in a later unit.
4. Supposing you were in space in a weightless environment, would it require a force to set an object in motion? Absolutely yes!
Even in space objects have mass. And if they have mass, they have inertia. That is, an object in space resists changes in its state of motion. A force must be applied to set a stationary object in motion. Newton's laws rule - everywhere!
5. Fred spends most Sunday afternoons at rest on the sofa, watching pro football games and consuming large quantities of food. What effect (if any) does this practice have upon his inertia? Explain.
Fred's inertia will increase! Fred will increase his mass if he makes a habit of this. And if his mass increases, then his inertia increases.
6. If the forces acting upon an object are balanced, then the object
a. must not be moving.
b. must be moving with a constant velocity.
c. must not be accelerating.
d. none of these
The answer could be A (but does not have to be A) and it could be B (but does not have to be B). An object having balanced forces definitely cannot be accelerating. This means that it could be at rest and staying at rest (one option) or could be in motion at constant velocity (a second option). Either way, it definitely is not accelerating - choice C of your four choices.
7. Determine the accelerations that result when a 12-N net force is applied to a 3-kg object and then to a 6-kg object.
A 3-kg object experiences an acceleration of 4 m/s/s. A 6-kg object experiences an acceleration of 2 m/s/s.
8. A net force of 15 N is exerted on an encyclopedia to cause it to accelerate at a rate of 5 m/s2. Determine the mass of the encyclopedia.
Use Fnet= m * a with Fnet = 15 N and a = 5 m/s/s.
So (15 N) = (m)*(5 m/s/s) And m = 3.0 kg
9. Suppose that a sled is accelerating at a rate of 2 m/s2. If the net force is tripled and the mass is doubled, then what is the new acceleration of the sled? Answer: 3 m/s/s
The original value of 2 m/s/s must be multiplied by 3 (since a and F are directly proportional) and divided by 2 (since a and m are inversely proportional)
10. Suppose that a sled is accelerating at a rate of 2 m/s2. If the net force is tripled and the mass is halved, then what is the new acceleration of the sled? Answer: 12 m/s/s
The original value of 2 m/s/s must be multiplied by 3 (since a and F are directly proportional) and divided by 1/2 (since a and m are inversely proportional)
11. While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?
Trick Question! Each force is the same size. For every action, there is an equal ... (equal!). The fact that the firefly splatters only means that with its smaller mass, it is less able to withstand the larger acceleration resulting from the interaction. Besides, fireflies have guts and bug guts have a tendency to be splatterable. Windshields don't have guts. There you have it.
12. For years, space travel was believed to be impossible because there was nothing that rockets could push off of in space in order to provide the propulsion necessary to accelerate. This inability of a rocket to provide propulsion is because ...
a. ... space is void of air so the rockets have nothing to push off of.
b. ... gravity is absent in space.
c. ... space is void of air and so there is no air resistance in space.
d. ... nonsense! Rockets do accelerate in space and have been able to do so for a long time.
It is a common misconception that rockets are unable to accelerate in space. The fact is that rockets do accelerate. There is indeed nothing for rockets to push off of in space - at least nothing which is external to the rocket. But that's no problem for rockets. Rockets are able to accelerate due to the fact that they burn fuel and push the exhaust gases in a direction opposite the direction which they wish to accelerate.
13. Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ...
a. greater than the acceleration of the bullet. b. smaller than the acceleration of the bullet.
c. the same size as the acceleration of the bullet.
The force on the rifle equals the force on the bullet. Yet, acceleration depends on both force and mass. The bullet has a greater acceleration due to the fact that it has a smaller mass. Remember: acceleration and mass are inversely proportional.

Newton’s Laws on Earth & Space

SEPyC expected learnings

Establece relaciones entre la gravitación, la caída libre y el peso de los objetos, a partir de situaciones cotidianas.
Describe la relación entre distancia y fuerza de atracción gravitacional y la representa por medio de una gráfica fuerza-distancia.
Identifica el movimiento de los cuerpos del Sistema Solar como efecto de la fuerza de atracción gravitacional.
Argumenta la importancia de la aportación de Newton para el desarrollo de la ciencia.

Remember: The FORCE (on an object) is a measure of the amount of a push or pull exerted on an object and it is measured in newtons.

01 Gravity

“Matter attracts matter in any region of the Universe” Sir Isaac Newton

What is mass?

It is incorrect to specify weight in any units other than newtons
Consumer items should have their contents labelled
Mass 10kg or Weight 100N

http://resources.yesican-science.ca/trek/mars2/final2/notes/new_notes.html

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FOR FRIDAY FOR FRIDAY FOR FRIDAY FOR FRIDAY FOR FRIDAY FOR FRIDAY

1. What is the difference between Gravity Force and Weight?

2. What two factors affect Gravity? How do they affect it?

3. Write five differences between MASS and WEIGHT?

4. What is the formula to get and object's weight?

5. Juanito has gone to Jupiter. He says that his mass is different there and his weight is greater? Is he right?

6. What can you do to lose weight without exercises, diet and discipline?

7. Complete the next table.

8. Draw a force vs distance graph using the next data

9. What is the importance of Gravity force in the heavenly bodies of the Solar System?

10. What is the importance of Newton's contribution to Science Development?

Trabajo de laboratorio

DIARIO GENERAL (Trabajo dentro del laboratorio)

1. USO MI BATA. Se presenta con la bata con nombre, limpia (cuello limpio)
2. CUIDO CABELLO. Las alumnas vienen con su cabello recogido, alumnos fajados y cabello corto. Nada de accesorios en las manos.
3. TRAIGO MATERIAL Trae el material indicado acordado con el equipo.
4. HAGO BUEN USO. Hace uso correcto del material y equipo de laboratorio.
5. SIGO PROCEDIMIENTO. Sigue el procedimiento con los pasos indicados.
6. PARTICIPO. Participa activamente en la práctica.
7. COLABORO. Apoya sus compañeros en el desarrollo de la práctica.
8. DISCUSIÓN. Discute con sus compañeros las preguntas finales.
9. RESPETO. Respeta a sus compañeros y obedece las instrucciones del profesor.
10. LIMPIO Y ORDENO. Mantiene limpio y ordenado el lugar de trabajo.

*Un alumno no puede abandonar el laboratorio si no cumple con el punto 10.

* Los alumnos sólo traen la bata el día en que tienen la práctica.
* Se dará punto extra a todos en DG si el grupo completo trae la bata.

EXAMEN (Reporte en el cuadernillo de Prácticas)

1. Lee con anterioridad la Práctica para formarse una idea general.
2. Contesta las preguntas iniciales basándose en una investigación bibliográfica, videográfica o en Internet.
3. Sigue el procedimiento indicado con orden.
4. Muestra sus resultados con dibujos.
5. Elabora y utiliza tablas y gráficas para interpretar resultados.
6. Responde las preguntas finales de manera acertada.
7. Comenta sus conclusiones con lo visto en clase.
8. Argumenta sus conclusiones relevantes relacionándolas con los conceptos y aplicaciones del tema vistos en clase.
9. Toma en consideración 3 fuentes de información para sustentar su reporte de prácticas.
10. Muestra una buena redacción(Ortografía/Caligrafía/Gramática)

*Los alumnos tienen una semana para entregar el reporte de prácticas

November Program

Newton's Laws of Motion

VISIT THIS PAGE FOR A MORE COMPLETE COVERAGE:
http://www.physicsclassroom.com/Class/newtlaws/
http://science.howstuffworks.com/science-vs-myth/everyday-myths/newton-law-of-motion.htm

Objetivo de la secuencia:
1. Interpreta y aplica las Leyes de Newton como un conjunto de
reglas para describir y predecir los efectos de las fuerzas en
experimentos y/o situaciones cotidianas.
2. Valora la importancia de las Leyes de Newton en la explicación de
las causas del movimiento de los objetos.


Introduction

Isaac Newton (a 17th century scientist) put forth a variety of laws that explain why objects move (or don't move) as they do. These three laws have become known as Newton's three laws of motion. The focus of Lesson 1 is Newton's first law of motion - sometimes referred to as the law of inertia.

NEWTON'S FIRST LAW OF MOTION - LAW OF INERTIA

Newton's first law of motion is often stated as

* An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.
* Every object persists in its state of rest or uniform motion­ in a straight line unless it is compelled to change that state by forces impressed on it.
* ­An object at rest will stay at rest, forever, as long as nothing pushes or pulls on it. An object in motion will stay in motion, traveling in a straight line, forever, until something pushes or pulls on it.


*Objects keep on donig what they are doing.

Applications:
1. A magician takes the table clothe without breaking the dishes.
2. When your automobile starts its motion, you move backward and if you brakes ypu go forward.
3. At "Recórcholis" there is a game wich uses discs that float over a table and continue in motion becasuse of the air that goes upward.
4. Blood rushes from your head to your feet while quickly stopping when riding on a descending elevator.
5. The head of a hammer can be tightened onto the wooden handle by banging the bottom of the handle against a hard surface.
5. A brick is painlessly broken over the hand of a physics teacher by slamming it with a hammer. (CAUTION: do not attempt this at home!)
6. To dislodge ketchup from the bottom of a ketchup bottle, it is often turned upside down and thrusted downward at high speeds and then abruptly halted.
7. Headrests are placed in cars to prevent whiplash injuries during rear-end collisions.
•While riding a skateboard (or wagon or bicycle), you fly forward off the board when hitting a curb or rock or other object that abruptly halts the motion of the skateboard.


Mass as a Measure of the Amount of Inertia

All objects resist changes in their state of motion. All objects have this tendency - they have inertia. But do some objects have more of a tendency to resist changes than others? Absolutely yes! The tendency of an object to resist changes in its state of motion varies with mass. Mass is that quantity that is solely dependent upon the inertia of an object. The more inertia that an object has, the more mass that it has. A more massive object has a greater tendency to resist changes in its state of motion

Physicists use the term inertia to describe this tendency of an object to resist a change in its motion. The Latin root for inertia is the same root for "inert," which means lacking the ability to move. So you can see how scientists came up with the word. What's more amazing is that they came up with the concept. Inertia isn't an immediately apparent physical property, such as length or volume. It is, however, related to an object's mass. To understand how, consider the sumo wrestler and the boy example in "How stuff works"

Which person in this ring will be harder to move? The sumo wrestler or the little boy?

Inertia: the resistance an object has to a change in its state of motion (constant velocity or repose).
Inertia: tendency of an object to resist changes in its velocity
Inertia: tendency of an object to resist accelerations


NEWTON´S SECOND LAW OF MOTION - LAW OF ACCELERATION F = MA

Newton's second law of motion can be formally stated as follows:

*The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.
*­When a force acts on an object, the object accelerates in the direction of the force. If the mass of an object is held constant, increasing force will increase acceleration. If the force on an object remains constant, increasing mass will decrease acceleration. In other words, force and acceleration are directly proportional, while mass and acceleration are inversely proportional.
*For a constant mass, force equals mass times acceleration

So what can you do with Newton's second law? As it turns out, F = ma lets you quantify motion of every variety. Let's say, for example, you want to calculate the acceleration of the dog sled shown below.

If you want to calculate the acceleration, first you need to modify the force equation to get a = F/m. When you plug in the numbers for force (100 N) and mass (50 kg), you find that the acceleration is 2 m/s2.

Now let's say that the mass of the sled stays at 50 kg and that another dog is added to the team. If we assume the second dog pulls with the same force as the first (100 N), the total force would be 200 N and the acceleration would be 4 m/s2

Notice that doubling the force by adding another dog doubles the acceleration. Oppositely, doubling the mass to 100 kg would halve the acceleration to 2 m/s2.

Finally, let's imagine that a second dog team is attached to the sled so that it can pull in the opposite direction

If two dogs are on each side, then the total force pulling to the left (200 N) balances the total force pulling to the right (200 N). That means the net force on the sled is zero, so the sled doesn’t move

How do we measure forces?

1 Newton = 1 Kg * m/s^2

The definition of the standard metric unit of force is stated by the above equation. One Newton is defined as the amount of force required to give a 1-kg mass an acceleration of 1 m/s/s.

*Even today people still believe that a force is required to keep an object moving.

Newton's Third Law of Motion - LAW OF FORCE PAIRS

Newton's third law is probably the most familiar. Everyone knows that every action has an equal and opposite reaction, right? Unfortunately, this statement lacks some necessary detail. This is a better way to say it:

*A force is exerted by one object on another object. In other words, every force involves the interaction of two objects. When one object exerts a force on a second object, the second object also exerts a force on the first object. The two forces are equal in strength and oriented in opposite directions.

*For every action, there is an equal and opposite reaction.

*The statement means that in every interaction, there is a pair of forces acting on the two interacting objects.
*The size of the forces on the first object equals the size of the force on the second object.
*The direction of the force on the first object is opposite to the direction of the force on the second object.
*Forces always come in pairs - equal and opposite action-reaction force pairs.

Examples

1. Propulsion of a fish through the water.
2. Flying motion of birds
3. You move your feet backward. Your body moves forward
4. Motion of a car on the way to school
5. Interaction between a baseball bat and a baseball
6. Baseball pushes glove leftwards. The glove pushes the baseball rightward.
7. Bowling ball pushes pin leftwards. Pin pushes bowling ball rightward
8. Enclosed air particles push balloon wall outwards. Balloon wall pushes enclosed air particles inwards

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1. Imagine a place in the cosmos far from all gravitational and frictional influences. Suppose that you visit that place (just suppose) and throw a rock. The rock will
a. gradually stop.
b. continue in motion in the same direction at constant speed.

2. A 2-kg object is moving horizontally with a speed of 4 m/s. How much net force is required to keep the object moving at this speed and in this direction?

3. Mac and Tosh are arguing in the cafeteria. Mac says that if he flings the Jell-O with a greater speed it will have a greater inertia. Tosh argues that inertia does not depend upon speed, but rather upon mass. Who do you agree with? Explain why.

4. Supposing you were in space in a weightless environment, would it require a force to set an object in motion?

5. Fred spends most Sunday afternoons at rest on the sofa, watching pro football games and consuming large quantities of food. What effect (if any) does this practice have upon his inertia? Explain.


6. If the forces acting upon an object are balanced, then the object

a. must not be moving.
b. must be moving with a constant velocity.
c. must not be accelerating.
d. none of these

7. Determine the accelerations that result when a 12-N net force is applied to a 3-kg object and then to a 6-kg object.

8. A net force of 15 N is exerted on an encyclopedia to cause it to accelerate at a rate of 5 m/s2. Determine the mass of the encyclopedia.

9. Suppose that a sled is accelerating at a rate of 2 m/s2. If the net force is tripled and the mass is doubled, then what is the new acceleration of the sled?

10. Suppose that a sled is accelerating at a rate of 2 m/s2. If the net force is tripled and the mass is halved, then what is the new acceleration of the sled?

11. While driving down the road, a firefly strikes the windshield of a bus and makes a quite obvious mess in front of the face of the driver. This is a clear case of Newton's third law of motion. The firefly hit the bus and the bus hits the firefly. Which of the two forces is greater: the force on the firefly or the force on the bus?

12. For years, space travel was believed to be impossible because there was nothing that rockets could push off of in space in order to provide the propulsion necessary to accelerate. This inability of a rocket to provide propulsion is because ...

a. ... space is void of air so the rockets have nothing to push off of.
b. ... gravity is absent in space.
c. ... space is void of air and so there is no air resistance in space.
d. ... nonsense! Rockets do accelerate in space and have been able to do so for a long time.

13. Many people are familiar with the fact that a rifle recoils when fired. This recoil is the result of action-reaction force pairs. A gunpowder explosion creates hot gases that expand outward allowing the rifle to push forward on the bullet. Consistent with Newton's third law of motion, the bullet pushes backwards upon the rifle. The acceleration of the recoiling rifle is ...

a. greater than the acceleration of the bullet.
b. smaller than the acceleration of the bullet.
c. the same size as the acceleration of the bullet.