Type:
Single
Objective:
Date: ______________
Work-Energy Review
Homework: Study for Test #4: Work-Energy
AP Physics
Date ___________
Mr. Mirro
Work-Energy Review
1. When a certain rubber band is stretched a distance X, it exerts a restoring force of
magnitude F = AX, where A is the elastic constant for the rubber band. The work
done by a person in stretching this rubber band from X = 0 to X = L is:
a) (AX)L
b) A + 2L
c) A + 2X
d) (AX2)  2
e) (AL2)  2
2. Which of the following objects has the largest kinetic energy ?
a) mass 3M
b) mass 3M and speed 2V
c) mass 2M and speed 3V
d) mass M and speed 4V
e) all have the same kinetic energy
3. As shown, a ball placed at point P of one end of a rough circular track is released from rest and slides
past the bottom of the track. Which is true of the height to which the block rises on the other side of
the track ?
a) it is equal to h/2 pi
b) it is equal to h/4
c) it is equal to h/2
d) it is equal to h
e) it is between 0 and h, the exact height depends
on how much energy is transferred to friction
P
h
4. As shown, an escalator is used to move 20 people (60 kg each) per minute
from the first floor of a department store to the second, 5 m above. The
power to do so is closest to:
a) 100 W
b) 200 W
c) 1000 W
d) 2000 W
e) 60,000 W
5m
30
5. The simple pendulum shown consists of a 2 kg mass attached to a string. When it is
released from rest at X, what is its speed at its lowest point, Y ? d
a) 0.90 m/s
b)
3.6 m/s
c) 3.6 m/s
d) 6.0 m/s
e) 36.0 m/s
X
1.85 m
Y
6. As shown, a 100 N block is towed up a 200 m incline at constant speed with force of 71 N. The
amount of thermal energy produced for the entire ascent is:
a) 2100 J
b) 2900 J
c) 4200 J
d) 13,200 J
e) 14,200 J
71 N
100 m
30
7. A 4.0 kg mass hangs on a spring and stretches it 0.05 m. The spring is then cut exactly in
half. The same 4.0 kg mass, when hung on this cut spring, will cause the spring to be stretched:
a) 0.05 m
b) 0.025 m
c) 0.10 m
d) 0.20 m
e) 0.40 m
8. A block of mass m slides on a horizontal frictionless table with an initial speed v. It then hits
and compresses a spring whose force constant is k, and is then brought to rest (it does not oscillate).
How much is the spring compressed from its original, equilibrium position ?
a) v 2
2g
b) mgv
k
c) mv
k
d) v m
 k
e) v k
 m
9. The work done by gravity during the decent of a projectile is:
a) positive
b) negative
c) zero
d) sign depends on the direction of the y-axis
e) sign depends on the direction of the x-axis
10. A block at point P is released from rest and slides down along the frictionless track as
shown. At point Q, its speed is:
P
a)  (H - h)
b) 2g (H - h)
d)  2g (H - h)
c) (H - h)
e) (H – h)2
2g
2g
Q
H
h
ground level
11. As shown, a 4.0 kg block rests on a flat, frictionless table and is attached to a massless spring which
obey’s Hooke’s Law. When a force of 20.0 N is applied to the spring-block “system,” the spring
compresses to 5.0 cm (?? meters) to the left.
a) On the axis below, plot the spring’s restoring force
as a function of spring compression and elongation
for values of x from –5.0 cm to +5.0 cm.
It is not necessary to show your work for this part.
4.0
kg
-5.0 cm
F = 20 N
0.0 cm
(equilibrium)
F (N)
x (cm)
b) From your plot, determine the work done on the spring during its compression from
–5.0 cm to its equilibrium position.
c) If the block is released from rest at -5.0 cm, determine the block’s speed as it goes
through equilibrium.
d) Carefully describe how the addition of a friction force on the surface will affect your
answer to part (c). Explain in detail without calculations.