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Practice TEST
WORK & ENERGY
PART I: MULTIPLE CHOICE
Read each question carefully. Choose the best answer that completes each question.
1.
Work is done when…
a. An object is at rest
b. A force is applied to an object.
c. A force causes an object to move.
d. Mr. Stanich thinks.
2.
Moe and Larry prevent Curley’s 7500 N car, with its brakes released, from rolling down a 50 m
hill by pushing on the car with a force of 250 N. How much work has Moe and Larry done on
Curley’s car?
a. 12,500 J
b. 375,000 J
c. 362,500 J
d. No work is done.
e. None of the previous.
3.
A 10 Kg object is dropped from a cliff 100 m high. At the midpoint of its fall, its total mechanical
energy is…
a. 19,600 J
b. 9800 J
c. 4900 J
d.
2450 J
e. 1000 J
4.
A truck weighs twice as much as a car, and is moving at twice the velocity of the car. Which
statement is true about the truck’s kinetic energy compared to that of the cars’?
a. The truck has 8 times the kinetic energy of the car.
b. The truck has 4 times the kinetic energy of the car.
c. The truck has twice the kinetic energy of the car.
d. The truck has the same kinetic energy of the car.
5.
Which of the following is the correct unit of work expressed in SI units?
a. Kgּm/s2 b. Kgּm2/s2 c. Kgּm2/s d. Kg2ּm/s2
6.
A spring is characterized by a spring constant of 60 N/m. How much elastic potential energy does
it store when stretched by 1 cm?
a. 3 x 10-3 J
b. 0.30 J
c. 60 J
d. 600 J
e. 30 J
7.
Sponge Bob Square Pants pulls Patrick in a sled on an icy surface (assume no friction), with a
force of 60 N at an angle of 37o upward from the horizontal. If he pulls Patrick a distance of 12 m,
what is the work done by Sponge Bob Square Pants?
a. 185 J
b. 433 J
c. 575 J
d. 720 J
e. There is no work done by Sponge Bob because he would never leave Bikini Bottom.
8.
A 1500 kg car accelerates from 0 - 25 m/s in 7 s. What is the horsepower delivered by the engine?
(1Hp=746W)
a. 60 Hp
b. 70 Hp
c. 80 Hp
d. 90 Hp
9.
Of the following, which is not a unit of power?
a. Watt/second
b. Newton-meter/second
c. Joule/second
d. Watt
10. A 0.50 kg sphere at the top of an incline has a potential energy of 6 J relative to the base of the
incline. Rolling halfway down the incline will cause the sphere’s potential energy to be ____.
a. 3 J
b. 0 J
c. 6 J
d. 12 J
11. What is the minimum power required for a conveyor to raise an 0.82 kg box 4 m vertically in 8 s?
a. 64 watts
b. 32 watts
c. 260 watts
d. 4 watts
e. 0.41 watts
12. Three people of equal mass climb a mountain using paths A, B, and C shown in the diagram
below. Along which path(s) does a person gain the greatest amount of gravitational potential
energy from start to finish?
a.
b.
c.
d.
B, only
C, only
A, only
The gain is the same along all paths.
13. A 600 N basketball player jumps 0.5m vertically off the floor. What is her kinetic energy just
before hitting the floor?
a. 30 J
b. 300 J
c. 60 J
d. 600 J
14. A 5 kg box slides down a frictionless incline of length 10 m. The incline makes an angle of 25 0 to
the ground. Find the speed of the box when it reaches the bottom of the incline.
a. 82.3 m/s
b. 14 m/s
c. 13 m/s
d. 9 m/s
e. none of the previous
For questions 15-17 refer to the following:
The diagram below represents a simple pendulum with a 2 kg bob and a length of 10 m. The
pendulum is released from a rest at position 1 and swings without friction through position 4. At
position 3, its lowest point, the speed of the bob is 6 m/s.
15. At which position does the bob have its maximum kinetic energy?
a. 1
b. 2
c. 3
d. 4
e. A
16. What is the potential energy of the bob at position 1 in relation to position 3?
a. 18 J b. 36 J
c. 180 J
d. 72 J
17. Compared to the sum of the kinetic and potential energies of the bob at position 1, the sum of the
kinetic and potential energies of the bob at position 2 is…
a. greater b. the same c. less
18. If the force acts _____ to the direction of the motion, then work is _____.
a. perpendicular; done
b. parallel; not done
c. parallel; done
d. perpendicular; no work
e. both c and d
19. A 1000 kg mass starts from rest and is accelerated by a 2000 N force for a distance of 100 m along
a horizontal frictionless surface. What is the acceleration of the mass? See diagram below.
a. 0.5 m/s2 b. 2.0 m/s2 c. 10 m/s2 d. 20 m/s2
PART II: ESSAY
Name ____________________________________ Date _____________________ Period _______
Read each question carefully. Answer each question in complete sentences. Please write legibly.
Points will be deducted if cannot read your handwriting.
1.
A compact car, which has a small mass and is being driven by Mr. Duncan, is carrying 4 big crates of
bowling balls and Mrs. Matlock who is driving a sports utility vehicle with a large mass Buick Rendezvous
is also carrying 4 crates of bowling balls. If both are traveling with the same velocity, then which one has
more kinetic energy and why? Explain.
2.
If two identical bowling balls are raised to the same height, one on Earth, the other on the Moon, does one
have a larger potential energy increase than the other and if so, then why? Explain.
3.
What conditions must be met so that work is actually done?
PART III: PROBLEMS A
Read each question carefully. You must show all of your work and equations used to receive full credit.
Be sure to draw diagrams and write neatly. Box and label all final answers with the correct units. Good
luck!!
1.
2.
Mr. Hanley is pulling his dog on a sled with a constant velocity on a level surface through a distance of 20
m. If the total mass of the sled and the dog is 45 kg and the coefficient of friction between the sled and the
snow is 0.25, how much work does Mr. Hanley do in pulling dog?
A cat fell from a 15m tree. The cat landed safely on a pile of leaves. Assuming that the cat has a mass of 9
kg and has a uniform velocity of 18 m/s, estimate the work done on the cat by the air resistance as he fell.
3.
A 1300 kg car rolls at a velocity of 2.54 m/s on a horizontal surface and strikes a horizontal coiled spring
and is brought to rest in a distance of 3 m. What is the spring constant of the coiled spring?
4.
What is the minimum amount of work done by friction that is needed to push a 900 kg car 800 m up along
a 150 incline, assume that the coefficient of friction affecting the car is 0.23?
5.
A roller coaster is shown in the figure below. Assuming no friction, calculate the speed at point C and D.
The coaster has an initial velocity of 1.8 m/s at point A.
A
C
25 m
D
12 m
4m
B
6.
A pendulum bob of length 50 cm is pulled 30 cm away from a vertical reference line and released from
rest.
(a) At what height, above the horizontal, is the pendulum bob released?
(b) What will be its maximum speed? Where can this speed be found on the path of the
pendulum’s swing?
7. On the diagram below a spring starts at rests and is compressed then released. Indicate the areas of
maximum potential energy and areas of maximum kinetic energy. Also, indicate which direction the force is
acting.
8. While working his summer job, Michael rolls a lawn roller across a lawn by a force of
115 N along the direction of the handle, which is 22.50 above the horizontal. If Michael
develops 64.6 W of power for 90 seconds, what distance is the roller pushed?
There will be a couple of bonus questions.