2.3 Energy Transfer Study Guide

2.3 Energy Transfer (8.2.3)

Explore this Phenomenon

As the boy skates down the ramp, he goes faster, when he skates up the ramp he goes slower.

1. What observations can you make about the skater?
2. What questions can you ask about the skater’s energy?
3. How can you explain what happens to the skater’s kinetic  energy?

8.2.3 Energy Transfer
Engage in argument to identify the strongest evidence that supports the claim that the kinetic energy of an object changes as energy is transferred to or from the object. Examples could include observing temperature changes as a result of friction, applying force to an object, or releasing potential energy from an object. (PS4.A) .

In this section, focus on energy and matter. Energy can be  transferred to or from objects and when it is transferred it often changes forms such as kinetic energy to heat energy or potential energy to kinetic energy.

Kinetic-Potential Energy Changes
Remember back to the Law of Conservation of Mass that states that matter cannot be created or destroyed. There is a similar law for energy. The Law of Conservation of Energy states that energy cannot be created or destroyed only transformed from one form into another or transferred from one object to another. One of the most common energy transformations occurs between kinetic and potential energy. Kinetic energy is the energy of moving objects. Potential energy is energy that is stored in objects, typically because of their position or shape. Kinetic energy can be used to change the position such as climbing to the top of a slide or shape of an object such as pulling back on a rubber-band, giving it potential energy. Potential energy gives the object the potential to move. If the potential energy is released then the object will move and change the potential energy back to kinetic energy.

To investigate how potential and kinetic energy are related in a roller coaster simulator, visit http://go.uen.org/b0t l

The man in the photo just finished coming down the water slide. When he was at the top of the slide, he had potential energy. Why? He had the potential to slide down into the water because of the pull of gravity. As he moved down the slide, his potential
energy changed to kinetic energy. By the time he reached the water, the potential energy had changed to kinetic energy.

How could the man regain his potential energy? He could climb up the steps to the top of the slide. It takes kinetic energy to climb the steps and this energy would be stored in his position on the stairs as he climbed. By the time he got to the top of the slide, he would have the same amount of potential energy as before.

Friction- the resistance of an object to movement, also causes changes in kinetic energy.

Rub your hands rapidly together. What do you feel? Friction causes the kinetic energy of the rubbing hands to be transformed to heat energy which is why
your hands feel warm. On a normal slide, friction would help convert some of the girl’s kinetic energy to heat energy. As her kinetic energy decreased, she would slow down. Since this is a water slide the water reduces friction, her kinetic energy won’t be
converted to heat as much and she can get going much faster.

Putting It Together

1. Explain how your understanding of the energy transfer has changed.
2. Think of another phenomenon that applies to transfer of energy.
3. Explain what happens to the skater’s energy as he skates up and down the hills in the skate park.
4. If the skater dragged his foot on the ground as he skates down the ramp, what will happen to his speed?
5. What would happen to his kinetic energy if he did this?
6. What evidence can you use to support your answer?