TEACHER ANSWER KEY

HOME ENERGY AUDIT: ENERGY WORKSHEET

DIRECTIONS: Answer the questions below in the space provided.

1. How are work and energy related?

Energy is required to accomplish a change in a system which is work. For example, moving an object is a change in a system and energy must be added to accomplish this change. Thus, work can only be accomplished if energy is expended.<

2. Circle the situation from each of the choices below that illustrates the greater amount of work:
 a. pushing a 40 kg shopping cart 10 m pushing a 40 kg shopping cart 100 m
 b. loading 300 kg of bricks into a truck loading 30 kg of bricks into a truck
 c. inserting a 10 cm screw into a board inserting a 7 cm screw into a board
 d. driving a Ferrari 22 km driving a Ferrari 100 km
3. Explain how kinetic energy and potential energy vary as a girl swings on a playground swingset.

At the top of the swing, all of the girl's energy is potential energy (energy of position) as the girl momentarily stops. As she begins to fall into the swing, this potential energy is converted into kinetic energy (energy of movement). The kinetic energy peaks at the bottom of the swing as the girl is no longer falling into the swing. On the up swing, the kinetic energy is converted back into potential energy (her position is higher). Thus, potential energy is transformed into kinetic energy which is then tranformed back to potential energy.

4. Identify the type of energy represented by the underlined word in each of the following:
 a.  an infrared lamp in a restaurant keeps food warm  _KINETIC ENERGY_________
 b.  a student listens to a portable CD player  _ELECTRICAL ENERGY____
 c.  a teacher talks loudly to a class to get their attention  _SOUND ENERGY_________
 d.  hamburger that has been eaten at lunch  _CHEMICAL ENERGY______

5. For electrons to flow in order to power a television, there must be a complete _CIRCUIT___.

6. Energy is measured in units called __JOULES_________.

7. Explain why a system that starts with 800 joules of energy, must have 800 joules even after several energy transformations.

According to the First Law of Thermodynamics, energy can neither be created nor destroyed. So all of the energy in a system must be accounted for somehow. It may not be in the same place or same form after several transformations, but it IS all there.

8. Make a list of the top five ways you think you use electrical energy. Find out which one(s) really use the most.

Answers may vary depending on student lifestyle, background, or situation.