AP Physics Energy Practice Test
Answers: C,E,C,E,D,B,A,C,C,B,B,A,C,B,D 16. (a) 62.7 J (b) -15.1 J (c) -47.6 J (d) 47.6 J (e) 4.2 m/s
17. (a) 450 N (b) 135 J (c) 8.2 m/s (d) 9.49 m/s (e) 9.18 m
Directions: You may write on this sheet. For multiple choice write the CAPITAL letter of the best
response in the space provided. Answer the other questions in the space provided as completely and as
neatly as you can. Show your work and box in your final answers. Use g=9.8 m/s2 and neglect air
resistance unless instructed otherwise.
_____1. A bucket falls off a 100m high ledge. The bucket's speed when it is 60 m above the ground is
A. 6 m/s.
B. 17 m/s.
C. 28 m/s.
D. 34 m/s.
E. not enough information.
_____2. A 4 kg block is moving at 12 m/s on a horizontal frictionless surface. A constant force is
applied that slows it with an acceleration of 3 m/s/s. How much work must this force do to stop the
block?
A. 360 J.
B. -360 J.
C. 576 J.
D. -576 J.
E. -288 J.
_____3. A 6.5 kg object encounters a changing force that is graphed Vs distance below. How much
work was done on the object by this force?
A. 30 J.
B. 60 J.
C. 70 J.
D. 80 J.
E. 100 J.
_____4. A helicopter rescues a 105 kg shipwreck survivor by lifting him straight up. The survivor
moves 15 m up while his speed drops from 4 m/s to 0. What is the work done on him by the applied
force?
A. 840 J.
B. 13755 J.
C. 15435 J.
D. 16275 J.
E. 14595 J.
_____5. A roller coaster is at the top of hill A going 15 m/s. What will be its speed at the top of hill C?
A. 8 m/s.
B. 17 m/s.
C. 37 m/s.
D. 40 m/s.
E. 55 m/s.
_____6. An object of mass m is lifted at constant velocity a vertical distance H in time T. The power
supplied by the lifting force is
(A) mgHT
(B) mgH/T
(C) mg/HT
(D) mgT/H
(E) zero
_____7. A system consists of two objects having masses ml and m2 (ml < m2). The objects are
connected by a massless string, hung over a pulley as shown below, and then released. When the object
of mass m2 has descended a distance h, the potential energy of the system has decreased by
A. (m2 - ml)gh.
B. m2gh.
C. (m1 + m2)gh.
D. ½(ml + m2)gh.
E. 0.
_____8. A person pushes a box across a horizontal surface at a constant speed of 0.5 meter per second.
The box has a mass of 40 kilograms, and the coefficient of sliding friction is 0.25. The power
supplied to the box by the person is
(A) 0.2 W
(B) 5 W
(C) 50 W
(D) 100 W
(E) 200 W
_____9. From the top of a 70-meter-high building, a l-kilogram ball is thrown directly downward with
an initial speed of 10 meters per second. If the ball reaches the ground with a speed of 30 meters
per second, the energy lost to friction is most nearly
(A) 0J
(B) 100 J
(C) 300 J
( D) 400 J
(E) 700 J
_____10. A ball is thrown upward. At a height of 10 meters above the ground, the ball has a potential
energy of 50 joules (with the potential energy equal to zero at ground level) and is moving upward
with a kinetic energy of 50 joules. Air friction is negligible. The maximum height reached by the
ball is most nearly
(A) 10 m
(B) 20 m
(C) 30 m
(D) 40 m
(E) 50 m
_____11. A force F is exerted by a broom handle on the head of the broom, which has a mass
m. The handle is at an angle θ to the horizontal, as shown below. The work done by the
force on the head of the broom as it moves a distance d across a horizontal floor is
(A) Fd sin θ (B) Fd cosθ
(C) Fm cosθ (D) Fm tanθ
(E) Fmd sinθ
_____12. A descending elevator of mass 1,000 kg is uniformly decelerated to rest over a distance of 8
m by a cable in which the tension is 11,000 N. The speed vi of the elevator at the beginning of the 8
m descent is most nearly
(A) 4 m/s
(B) 10 m/s
(C) 13 m/s
(D) 16 m/s
(E) 21 m/s
_____13. After a spring is compressed 0.2 m from its uncompressed length it exerts a 20 N force on a
0.4 kg block resting on a horizontal frictionless surface. After it is released the block will reach a
maximum velocity of
A. 2.1 m/s.
B. 100.0 m/s.
C. 3.2 m/s.
D. 10.0 m/s.
E. 6.3 m/s.
_____14. Shown below are 3 frictionless ramps of equal height. An identical block slides from rest
down each ramp to the bottom. Indicate which statements below are true.
I. Ramp B will have the greatest speed.
II. Ramp C will have the greatest time.
III. Ramp A will have the same time as ramp C.
A. Statement I only.
B. Statement II only.
C. Statements I and II only.
D. Statement III only.
E. Statements I and III only.
_____15. Three rocks are thrown from a 40 m high cliff, Rock A is thrown at 10 m/s 30o above the
horizontal, Rock B is thrown 10 m/s horizontally, and Rock C is thrown 10 m/s 30o below the
horizontal, which rock hits the ground with the greatest speed?
A. C
B. B
C. A
D. All 3 hit with the same speed
E. A and C tie, B is slower
16. (10 Points) The system shown below is initially at rest. The incline is at an angle of θ = 40o to the
horizontal and friction is negligible. Block m1 is 4 kg and descends a distance h = 1.6 m to the floor.
Block m2 is 1.5 kg and is connected to block m1 by a string of negligible mass. The pulley has
negligible friction and mass. Answer the following questions.
(a) What is the work done on block m1 by its weight?
(b) What is the work done on block m2 by its weight?
(c) What is the change in potential energy of the 2-block system?
(d) What is the change in kinetic energy of the 2-block system?
(e) What is the speed of block m1 just before it reaches the floor?
17. (10 Points) A massless spring with force constant k = 750 N/m is fastened at its left end to a
vertical wall as shown in the figure below. A 3 kg block is pushed so it compresses the spring 0.6 m
from its uncompressed length. The figure below shows the situation before the spring is compressed.
A
B
C
Friction
0.3 m
0.6 m
x=0
(a) Determine the force of the spring on the block when the spring is compressed 0.6 m.
(b) Determine the elastic potential energy stored in the spring when it is compressed 0.6 m.
The block is released from rest when the spring is compressed 0.6 m and is pushed along a horizontal
frictionless surface by the spring.
(c) Determine the speed of the block at point A, when the spring is still compressed 0.3 m.
(d) Determine the speed of the block at point B, after the spring is no longer compressed.
The block encounters a surface with a coefficient of friction µk = 0.5 at point C.
(e) Determine how far the block moves beyond point C.