1. Energy Unit Test Review Answers

2. Energy Unit Test Review Answers
1. What force causes an object to have potential energy?
Gravity
2. Kinetic energy is energy of ____________________________.
motion
3. There are two things that affect an object’s kinetic energy. They are m_________ and s_________.
mass. speed.

3. Energy Unit Test Review Answers
4. Kinetic energy increases as both m_______ and s__________ _______________________________. (increase or decrease)
mass. speed. increase

4. 5. Which one has more kinetic energy, a person walking, a person running, or a person riding a bicycle? Why?
Person riding a bicycle
because person riding a
bicycle has the most speed.

5. Energy Unit Test Review Answers
6. If a bowling ball and a soccer ball are both moving at the same speed, which one will have more kinetic energy? Why?
Bowling ball
Because the bowling ball has
more mass.

6. Energy Unit Test Review Answers
7. If you pick up a grocery bag from the floor and put in on the table, you increase its potential energy. Explain how.
Grocery bag
Because the grocery bag is
farther off of the ground.

7. Energy Unit Test Review Answers
8. Label the pictures below as either Kinetic or Potential energy. Then, explain why. 8a. Kinetic energy Because the arrow is moving. a. b.

8. Energy Unit Test Review Answers
8. Label the pictures below as either Kinetic or Potential energy. Then, explain why. 8b. potential energy Because the bow string is pulled tight and not moving. a. b.

9. Energy Unit Test Review Answers
If you wrap a fur coat around a
thermometer. Will its temperature
rise? Explain why or why not.
No.
Because heat never comes from warm clothes.

10. Energy Unit Test Review Answers
10. If you hold one end of a metal nail against a piece of ice, the end in your hand soon becomes cold. Does cold flow from the ice to your hand? Or does heat flow from your hand to the ice? Explain.
Heat flows from your hand to the ice. Your hand feels cold because of the large temperature difference between your hand and the nail.

11. Energy Unit Test Review Answers
11. Heat transfer is a slow
process, meaning it doesn’t
happen very quickly. Explain why
“firewalkers” can walk safely
across a bed of red-hot coals in bare feet.
Heat transfer is slow process. So the firewalker’s feet do not feel hot as long as he does not stop walking.

12. Energy Unit Test Review Answers
12. If you drop a hot rock into a pail of water, the temperature of the rock and the water will change until both are equal. The rock will cool and the water will warm. Is this true if the rock is dropped into the Atlantic
Ocean?
Yes because heat always flows
from hot to cool. But since the Atlantic Ocean is so big, the temperature increase is not noticed.

13. Energy Unit Test Review Answers
13. When you step out of a swimming pool on a hot, dry day, you feel quite chilly. Why?
Some of your body’s thermal
energy has been transferred to
the pool water. There is now a
larger temperature difference
between your skin and the hot air, making you
feel chilly.

14. Energy Unit Test Review Answers
14. You have 2 beakers of water. Beaker 1 is at 110°C and Beaker 2 is at 45°C. Which picture correctly shows which way the heat will flow? Beaker 1 → Beaker 2 2
45°C 2
45°C 1
110OC 1
110OC

15. Energy Unit Test Review Answers
15. Next to each example, tell what kind of heat transfer is taking place:
Radiation, Conduction, or
Convection. Then, explain
why.
15a.
Conduction
Because the thermometer
is touching your tongue, transferring the heat.

16. Energy Unit Test Review Answers
15b.
Radiation
Infrared waves are
thermal, so we can
feel them from a
fireplace.

17. Energy Unit Test Review Answers
15c. Conduction and Convection. 1. Hot air in the oven touches the glass pan, which transfers the heat to the brownies that the glass pan touch. 2. Air in the oven touches the coils, rises, and then falls onto the top of the brownies.

18. Energy Unit Test Review Answers
15d. Conduction Hot cocoa touches the spoon and transfers the heat.

19. Energy Unit Test Review Answers
15e. Convection Just like in an oven or in the atmosphere, hot water rises and cold water sinks.

20. Energy Unit Test Review Answers
Convection
Hot air in the room rises, and then falls as it cools.

21. Energy Unit Test Review Answers
Conduction
Heat from your hand
flows to the ice cube.