Download Name: Period: _____ Date

Name: ___________________________________ Period: _____ Date: ____________________
Ch 12 Pretest: Work, Power,
Energy
Part 1: Matching. Place the letter of the best word by each definition.
1. _______ The unit used to measure energy
1 N . 1m
2. _______ energy from fission (splitting atoms)
or fusion (combining atoms)
3. _______ the ability to do work
4. _______ no energy can get in our out or the
amount is so small it can be ignored
5. _______ exerting a force for a distance; F x d
6. _______ heat energy, usually made from friction
7. _______ the amount of useful work a system
does; what energy is not lost to
“useless” forms (heat, sound)
8. _______ when energy can freely enter or
leave a system
9. _______ light energy, like from the sun
A. closed system
B. efficiency
C. elastic potential energy
D. gravitational potential
energy
E. kinetic energy
F. Joules
G. Law of conservation
of energy
H. nuclear energy
I. open system
J. power
K. radiant energy
L. thermal energy
M. Watts
N. work
O. energy
10. _______ energy stored by compressing or stretching something
11. _______ energy can not be created or destroyed; it only changes form
12. _______ units used to measure power; equal to 1 J/1 s
13. _______ energy when something is in motion
14. _______ the work you do and the amount of time in which you do it W/t
15. _______ energy of position; energy due to where you are
Use the formula W = F x d to solve the following equations. Show your work and be
sure to use correct units and sig figs.
16. _____________________ Joan moves her dresser, which weighs 53 N a distance of
4.32 m. How much work did she do?
17. _____________________ Felippe did 175.64 J of work moving an object 9.17 m. How
much mass does the object have?
18. Jose moves a box 5 m with 60 N of force in 10 seconds. Felicia pushes against a
car, for 3 minutes, but fails to move it. Who did more work? Explain.
19. In the problem above, who used more power, Jose or Felicia? Explain.
Use the formula P = W/t to solve the following equations. Show your work and be
sure to use correct units and sig figs.
20. _____________________ Gorge did 5150 J of work in 73 seconds. How much power
did he use?
21. _____________________ Antoinette’s car used 45,166W of power to do 432.5 J of
work. How long did it take?
22. – 23. What is efficiency of a system and how can we improve it (in general and
specifically)?
24. How are energy and work related?
A parked car starts at the top of a hill and rolls down and up the other side, equally
as high….
25. – 26. Does it reach the top? Explain.
27. – 28. Where does it have the most gravitational potential energy? Explain
29. – 30. Where does it have the least gravitational potential energy? Explain.
31. – 32. Where does it have the most kinetic energy? Explain
33. – 34. Where does it have the least kinetic energy? Explain.
35. – 37. I’m going bowling. I pick up the ball, go through my approach and throw it.
It hits the pins and I get 9. Describe all the forms of energy involved and what
makes them change form (what does the work).
Use the following formulas for the following problems. Show your work and use the
correct units and sig figs. Use 10.0 m/s2 for the acceleration due to gravity.
KE = ½ mv2
GPE = mgh
EPE = ½ kx2
38. _____________________ In the problem above, if my ball has a mass of 7 kg and I
throw it 2.01 m/s, how much KE does it have?
39. _____________________ If I have a mass of 91 kg and I am 0.55 m above ground on
the Moon, what is my gravitational potential energy (g
on the moon is 1.6 m/s2)
40. _____________________ The spring constant of a certain spring is known to be
400. N/m. If I stretch the spring .75 m how much
EPE does it have?
41. _____________________ There’s a 1250 kg car at the top of a hill 75 m high. The
brake fails and it starts to roll. How fast will it roll at
the bottom if all GPE is converted into KE?
42. - 45. Label each type of energy as it is transformed to a new type of energy in the
picture below.
46. – 48. Label as many transformations of energy as you can in the picture below.
49. - 52.Name two places where energy is “lost.” Explain how/why it is “lost” and how
we can improve that.
Name: ___________________________________ Period: _____ Date: ____________________
Ch 12 Pretest: Work, Power,
Energy
Part 1: Matching. Place the letter of the best word by each definition.
F___ The unit used to measure energy
1. ___
1 N 1m
A. closed system
B. efficiency
or fusion (combining atoms)
C. elastic potential energy
D. gravitational potential
.
H__ energy from fission (splitting atoms)
2. ___
O___ the ability to do work
3. ___
A___ no energy can get in our out or the
4. ___
amount is so small it can be ignored
N___ exerting a force for a distance; F x d
5. ___
L___ heat energy, usually made from friction
6. ___
B___ the amount of useful work a system
7. ___
does; what energy is not lost to
“useless” forms (heat, sound)
I
8. ___ ___ when energy can freely enter or
leave a system
energy
E. kinetic energy
F. Joules
G. Law of conservation
of energy
H. nuclear energy
I. open system
J. power
K. radiant energy
L. thermal energy
M. Watts
N. work
O. energy
K___ light energy, like from the sun
9. ___
C___ energy stored by compressing or stretching something
10. ___
G___ energy can not be created or destroyed; it only changes form
11. ___
M___ units used to measure power; equal to 1 J/1 s
12. ___
E___ energy when something is in motion
13. ___
J___the work you do and the amount of time in which you do it W/t
14. ___
D___
15. ___
energy of position; energy due to where you are
Use the formula W = F x d to solve the following equations. Show your work and be
sure to use correct units and sig figs.
230 J______ Joan moves her dresser, which weighs 53 N a distance of
16. ___
W=Fxd
4.32 m. How much work did she do?
53 x 4.32
228.96
(2 sf)
19.2 N _____ Felippe did 175.64 J of work moving an object 9.17 m. How
17. ____
W=Fxd
much mass does the object have?
175.64 = F x 9.17
19.15376227
(div by 9.17)
(3 sf)
18. Jose moves a box 5 m with 60 N of force in 10 seconds. Felicia pushes against a
car, for 3 minutes, but fails to move it. Who did more work? Explain.
Jose did 60 x 5 = 300J
Felicia did 0 N, because the car didn’t move
19. In the problem above, who used more power, Jose or Felicia? Explain.
Jose used 300/10 = 30 W
Felicia used 0 W (because she did 0 work)
Use the formula P = W/t to solve the following equations. Show your work and be
sure to use correct units and sig figs.
71 W______ Gorge did 5150 J of work in 73 seconds. How much power
20. ____
P = W/t
did he use?
5150/73
70.54794521 (2 sf)
.009576 s ________ Antoinette’s car used 45,166W of power to do
21. _______
432.5 J of work. How long did it take?
P = W/t
45,166 = 432.5/t
45,166t = 432.5
(mult by t)
(div by 45,166)
.009575787
(4 sf)
22. – 23. What is efficiency of a system and how can we improve it (in general and
specifically)?
A measure of energy “lost” due to friction
If you decrease friction, you increase
efficiency…use oil, smooth surfaces, etc.
to improve.
24. How are energy and work related?
Energy and work are “opposites sides of the
same coin” you use energy to do work.
We measure energy by the amount of work
done. That’s why they use the same
units… J.
A parked car starts at the top of a hill and rolls down and up the other side, equally
as high….
25. – 26. Does it reach the top? Explain.
No. It “loses” some of its energy to heat
and sound because of friction and air
resistance.
27. – 28. Where does it have the most gravitational potential energy? Explain
At the top of the hill…it’s the highest
up.
29. – 30. Where does it have the least gravitational potential energy? Explain.
At the bottom of the hill. It’s the lowest
point.
31. – 32. Where does it have the most kinetic energy? Explain
At the bottom of the hill. It’s moving the
fastest.
33. – 34. Where does it have the least kinetic energy? Explain.
At the top, before it moves. It has 0 J of
KE if it’s not moving.
35. – 37. I’m going bowling. I pick up the ball, go through my approach and throw it.
It hits the pins and I get 9. Describe all the forms of energy involved and what
makes them change form (what does the work).
Chemical  kinetic
I do work on the ball to pick it up, move and
throw it
Kinetic (ball)  kinetic (pins)
The ball does work to make the pins move
Kinetic (ball)  Sound
Friction does work to make sound
Use the following formulas for the following problems. Show your work and use the
correct units and sig figs. Use 10.0 m/s2 for the acceleration due to gravity.
KE = ½ mv2
GPE = mgh
EPE = ½ kx2
10 J_________ In the problem above, if my ball has a mass of 7 kg and I
38. ______
throw it 2.01 m/s, how much KE does it have?
2
KE = ½ mv
= .5 (7) (2.01)2 *** order of operations
says you do the square first!***
= 14.14035
(1 sig fig)
80. J______ If I have a mass of 91 kg and I am 0.55 m above ground on
39. _______
the Moon, what is my gravitational potential energy (g
on the moon is 1.6 m/s2)
GPE = mgh
= (91)(1.6)(.55)
= 80.08
(2 sig figs)
110 J ________ The spring constant of a certain spring is known to be
40. ________
400. N/m. If I stretch the spring .75 m how much
EPE does it have?
2
EPE = ½ kx
= .5 (400)(.75)2 *** order of operations
says you do the square first!***
= 112.5
(2 sig figs)
39 m/s______ There’s a 1250 kg car at the top of a hill 75 m high. The
41. _____
brake fails and it starts to roll. How fast will it roll at
the bottom if all GPE is converted into KE?
GPE = KE
mgh = ½ mv2
(1250)(10.0)(75) = .5(1250)v2 *** note
that since mass is on both sides, it
cancels out.
750 = .5v2
1500 = v2
v = 38.72983346
(2 sig figs)
42. - 45. Label each type of energy as it is transformed to a new type of energy in the
picture below.
picture is already labeled
here
46. – 48. Label as many transformations of energy as you can in the picture below.
B
D
C
A
A
B
C
D
chemical to heat and light
heat to kinetic
kinetic to electrical
electrical to light and heat
49. - 52.Name two places where energy is “lost.” Explain how/why it is “lost” and how
we can improve that.
A
Heat lost to radiation
Insulate the boiler
B
lost to heat through friction
Oil the machine
C
lost to heat through friction
Oil the machine