1. Energy
Chapter 7

2. Answer all questions on the Test review half sheet.
Bell Work
Answer all questions on the Test review half sheet.

3. 7.1 What is energy?
Energy measures the ability for things to change themselves or to cause change in other things.
Some examples are changes in temperature, speed, position, pressure, or any other physical variable.

4. 7.1 Units of energy
Pushing a 1-kilogram object with a force of one newton for a distance of one meter uses one joule of energy.
A joule (J) is the S.I. unit of measurement for energy.
One joule is a pretty small amount of energy.

5. Energy is measured in:
a. newtons.
b. joules.
c. kg/m2
d. kg•m/s2

6. Energy Conservation Energy cannot be created.
Energy cannot be destroyed.
Energy can be converted from one form to another.

7. Kinetic Energy
Energy of motion
KE = ½ mv2

8. What do we call energy of motion?
A. thermal energy
B. kinetic energy
C. potential energy
D. work energy

9. If you double your speed, your kinetic energy becomes:
A. 2 times smaller.
B. 4 times smaller.
C. 2 times bigger.
D. 4 times bigger.

10. What happens to the kinetic energy of an object if you double the mass?
A. 2 times smaller.
B. 4 times smaller.
C. 2 times bigger.
D. 4 times bigger.

11. Work and Potential Energy
The work done on the ball gives the ball gravitational potential energy.
Gravitational potential energy = mgh

12. Gravitational Potential Energy
Energy stored in an object due to its position.
GPE = m g height

13. An object’s gravitational potential energy is directly related to all of the following EXCEPT
A. Mass
B. Speed
C. Height
D. Gravity

14. Where does the ball have the most Gravitational Potential Energy?C. D.

15. Where does the ball have the most Kinetic Energy?

16. Bill lifts a 25-kg child from the ground onto a 1. 5 meter high table
Bill lifts a 25-kg child from the ground onto a 1.5 meter high table. What is the potential energy of the child?
A J
B J
C J
D. None! A child never has potential energy.

17. How high would you need to lift a 5-kg box to increase its potential energy by 1000 joules?
A. about 5000 m
B. about 500 m
C. about 200 m
D. about 20 m

18. Elastic Potential Energy
Energy stored in an object due to its shape.
The work done changing the shape of an object is stored elastic potential energy.

19. A stretched rubber band has
A. elastic potential energy.
B. Mechanical potential energy.
C. Chemical potential energy.
D. None of these

20. A wind-up toy has A. elastic potential energy.
B. Mechanical potential energy.
C. Chemical potential energy.
D. None of these

21. A compressed basketball has
A. elastic potential energy.
B. Mechanical potential energy.
C. Chemical potential energy.
D. None of these

22. Energy cannot be created or destroyed
Energy cannot be created or destroyed. Energy can be converted from one form to another. Is an example of
A. Newton’s first law
B. The law of conservation of energy
C. The pendulum law
D. None of these

23. Where does the pendulum have the most Pe? A B C D E
Where does the pendulum have the most Ke? A B C D E

24. Both Ball #1 and Ball #2 rolls down the hill
Both Ball #1 and Ball #2 rolls down the hill. Ball #1 goes on the steeper side. Compare the speed at the bottom.
a. Ball #1 has the greater speed.
b. Ball #2 has the greater speed.
c. The speed will be the same for both balls.
d. Not enough information is given.

25. A 2 Kg ball is released from rest at the top of a track and reaches a speed of 10 m/s at the bottom.
a. How much kinetic energy does the ball have?
b. How much potential energy does it have at the top of the hill (assuming no energy was lost)?
c. What was the height of the hill?

26. A 3 kg rock sits on a 0. 8 meter ledge
A 3 kg rock sits on a 0.8 meter ledge. If it is pushed off, how fast will it be going at the bottom?

27. A 4 kg ball is on a 5 m ledge. If it is pushed off the ledge, how much kinetic energy will it have just before hitting the ground?

28. How high up is a 3 kg object that has 300 joules of energy?

29. A rolling ball has 18 joules of kinetic energy and is rolling 3 m/s
A rolling ball has 18 joules of kinetic energy and is rolling 3 m/s. Find its mass.

30. A 4 kg bird has 8 joules of kinetic energy. How fast is it flying?

31. Match the Units F or Fw = ________ 8 w v = ______________ 8 N
W or E= __________
8 J
P = ______________
8 m/s