Energy

What is energy? Energy is something that can cause things to move or to change. Where is energy found? Energy can be found everywhere. How can you tell that an object has energy? When I see it move.

Energy is… The ability to perform work or to change an object.

Work is… The measurement of the energy used to perform a task.

Why is no work being done when someone is pushing a car but it is not moving? Work is only done when the object that is receiving the force moves from one location to another.

What is potential energy? The energy that is stored in the position or the structure of an object. Think of a stretched spring. It has energy, but it’s not moving. It has the potential to do work. The energy is stored.

Forms of potential energy Chemical potential energy Elastic potential energy Gravitational potential energy

What is chemical potential energy? This is the energy in the links between atoms and molecules. Food contains energy stored in the chemical bonds between atoms.

Elastic Potential Energy This is the energy stored by something that can stretch or compress. Name an example of this type of energy. A stretched rubber band A stretched slingshot Some watches

What is Gravitational Potential Energy? This is the energy an object possesses due to its position above Earth’s surface. Why is a boulder on a hill an example of gravitational potential energy? Anytime an object is raised above the ground, it gains gravitational potential energy.

A large boulder would have more gravitational potential energy. Why? Would a large boulder or a small boulder at the same height above the ground have more gravitational potential energy? A large boulder would have more gravitational potential energy. Why? The greater the object’s weight and height above the ground, the more gravitational energy it gains.

What do all the forms of potential energy have in common? All the forms of potential energy have the ability to do work. What is different about the types? The different forms of potential energy are due to different kinds of forces such as gravity, mechanical, and chemical.

A weight lifter lifts a barbell above her head and holds it there A weight lifter lifts a barbell above her head and holds it there. What can you infer about the work she is doing? Since the weights are not moving above the weight lifter’s head, she is not doing any work.

Gravitational potential energy What type of potential energy exists when you are on a diving board high above the swimming pool. Gravitational potential energy

What is kinetic energy? This is the energy of a moving object. What is an example of this type of energy? A moving car A rolling ball A roller coaster moving

The amount of kinetic energy an object has depends on the object’s velocity. An example is trying to knock down bowling pins with a tennis ball and with a bowling ball. Which ball would knock down more pins? The bowling ball of course! Why? Because the bowling ball has a greater mass than a tennis ball.

List some forms of kinetic energy. Heat- vibrations of particles. Electricity- related to the kinetic energy of electrons Sound- particles move in waves Light- moves in the form of waves

All forms of energy have one thing in common- they can perform WORK!

Can potential energy change to kinetic energy? Yes. Potential energy can easily change to kinetic energy. Think of a bow used to shoot arrows. The stretched bow has potential energy. As soon as the bow is released the potential energy changes to kinetic moving the arrow.

The ball moving at 5 m/s has more kinetic energy. Which has more kinetic energy- a ball moving at 4 m/s or a ball moving at 5 m/s? The ball moving at 5 m/s has more kinetic energy.

Which can do more work- a 3 kg bowling ball moving at 2 m/s or a 5 kg bowling ball moving at 2 m/s? The 5 kg bowling ball has more kinetic energy and can do more work.

A roller coaster stops at the top of a hill A roller coaster stops at the top of a hill. What can you infer about its kinetic energy? Since the roller coaster is not moving, it does not have any kinetic energy.

What is the law of conservation of energy? Scientists believe that energy cannot be created or destroyed; it only changes form. A roller coaster does not destroy energy as it slows down. The energy becomes heat and sound through the work of friction.

A dropped ball doesn’t bounce back to its starting height A dropped ball doesn’t bounce back to its starting height. How does this situation fit the law of conservation of energy? The dropped ball does not bounce back to its starting height because some of its kinetic energy has changed into heat and sound energy due to friction.

How might the heat energy in an oven perform both desirable and undesirable work? You might want the oven to do work by baking bread. On a hot summer day, the oven might also do undesirable work by adding more heat to a home that is already hot inside.