Name: ________________________ Class: ___________________ Date: __________
ID: A
Exam 3--PHYS 101--Fall07
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
____
____
1. A net force of 100 N acts on a 200 kg boulder, and a force of the same magnitude acts on a 10 g pebble. How
does the rate of change of momentum for the boulder compare to the rate of change of the pebble’s
momentum?
a. greater than
c. equal to
b. less than
d. not enough information
2. A cart is rolling along a frictionless track. Rain is falling into the cart. What happens to the momentum of
the cart? (assume the rain falls vertically into the cart)
a. increases
c. decreases
b. stays the same
d. not enough information
3. A uranium nucleus is at rest and undergoes fission and splits into two fragments, one heavy and one light.
Which of these statements is true?
a.
____
the lighter and heavier fragments have
c. the heavier fragment has a higher
the same velocity (but in opposite
velocity than the light one
directions)
b. the lighter and heavier fragments have
d. the lighter fragment has more momentum
the same momentum (but in opposite
than the heavy one
directions)
4. You have a mass of 90 kg, and you hold a gun with mass of 10 kg. You fire a 10 g bullet with a muzzle
velocity of 300 m/s. What is the magnitude of the velocity of you and the gun?
a.
b.
3 m/s
30 m/s
c.
d.
1
0.03 m/s
0.3 m/s
Name: ________________________
____
____
5. Superman catches Lois, who has a mass of 80 kg, as she falls from a skyscraper. Lois is traveling at 50 m/s,
and Superman brings her to a stop in 0.1 seconds. What is the magnitude of the force that Superman exerts
on Lois?
a. 800 N
c. 400 N
b. 40,000 N
d. 200,000 N
6. A collection of particles has a total kinetic energy of zero. What can we say about the momentum of the
system?
a.
b.
____
ID: A
the momentum is zero
the momentum is positive
c.
d.
the momentum is negative
the momentum is either positive of
negative, depending on the mass of the
particles
7. Which of these statements are true for elastic collisions:
I. Momentum is conserved
II. Energy is conserved
III. Energy is lost to sound, heat, and deformation.
IV. Momentum is not conserved
____
____
a. I and II
b. I and III
8. Which of these is an inelastic collision?
a. Two ping-pong balls colliding
b. Tennis ball bouncing off a bowling ball
9. What are the units for momentum?
a.
b.
Joules
kg m/s2
c.
d.
III and IV
I, II, and III
c.
d.
Two cars colliding
All of these
c.
d.
kg m/s
N•m
2
Name: ________________________
ID: A
____ 10. Kaisa sits on the outer rim of a merry-go-round, and Chad sits midway between the rim and center. The
merry-go-round makes 1 revolution every 2 seconds. Chad’s linear or tangential velocity is ...
a. four times Kaisa’s
d. same as Kaisa’s
b. one-half of Kaisa’s
e. twice Kaisa’s
c. one-quarter of Kaisa’s
____ 11. An object at rest begins to rotate with a constant angular acceleration. If this object rotates through an angle
θ in time t, what angle does it rotate through in twice that time?
a. 2θ
c. θ/2
b. 4θ
d. θ/4
____ 12. A car rounds a curve on a flat road. The coefficient of static friction between the road and tires is 0.70
(fs=µsmg). If the curve has a radius of 50. meters, what is the maximum safe speed at which the car can
round the curve?
a. 340 m/s
c. 19 m/s
b. 35 m/s
d. 71 m/s
____ 13. A wheel rotates as shown in this figure. What is the direction of the angular velocity vector ( ω)?
a.
b.
to the right
out of the page
c.
d.
3
into the page
to the left
Name: ________________________
ID: A
____ 14. In 1.2 seconds, a car accelerates from rest to 12 m/s. The radius of the car’s tire is 0.5 meters. What is the
angular acceleration, in revolutions per second 2, of one of the car’s tires?
a. 7 rev/s2
c. 3 rev/s2
2
b. 10 rev/s
d. 20 rev/s2
____ 15. A dentist’s drill starts at rest and undergoes an angular acceleration of 10 rad/s 2 for 3 seconds. Through what
angle, in radians, does the drill turn in this time?
a. 3 rad
c. 50 rad
b. 30 rad
d. 90 rad
____ 16. A centrifuge is used to separate the red blood cells from plasma. The radius of rotation is 10.0 cm, and the
rate of rotation is 100 rev/s. In a given sample, the mass of the red blood cells is 2 ×10-16 kg. What force is
required to separate the red blood cells from the plasma?
a. 2×10-15 N
b. 8×10-12 N
____ 17. How many revolutions is 400 degrees?
a.
b.
2500 rev
1.1 rev
c.
d.
10 N
2×10-11 N
c.
d.
64 rev
144,000 rev
4
Name: ________________________
ID: A
____ 18. Two spheres have the same mass. One sphere is made of aluminum, while the other sphere is made of gold.
Both are solid. Because gold is more dense, the radius of the gold sphere is smaller than the aluminum
sphere. Which has the larger moment of inertia?
a. gold sphere
c. both the same
b. aluminum sphere
d. not enough information
____ 19. This figure shows an arrangement of 3 particles rotating about a common axis. The axis bisects the 2 kg
mass. The 4 kg mass is 3 m from the axis, and the 5 kg mass is 2 m from the axis. What is the moment of
inertia?
a.
b.
56 kg m2
24 kg m2
c.
d.
5
22 kg m2
28 kg m2
Name: ________________________
ID: A
____ 20. This bar is rotating about the point O. What is the net torgue?
a. 9 N·m CW
d. 30 N·m CCW
b. 9 N·m CCW
e. None of these
c. 30 N·m CW
____ 21. When a cassette tape is played on a tape deck, there is tension in the tape that applies a torque to the supply
reel. Assuming the tension remains constant, how does the applied torque change as the supply reel becomes
empty?
a.
b.
torque remains constant
torque increases
c.
d.
6
torque decreases
not enough information
Name: ________________________
ID: A
____ 22. A merry-go-round has a mass of 200 kg and a radius of 2 m. It accelerates up to an angular velocity of 0.5
revolutions/second, with an acceleration of 0.02 rev/s 2. What work is required to bring the merry-go-round
up to this speed?
a. 2000 J
c. 4 J
b. 200 J
d. 50 J
____ 23. This figure shows the human arm. The forearm rotates about the elbow (point O), and the biceps exerts a
force on the ulna at 0.03 m from the elbow. The total length of the forearm and hand is 0.35 m. What force
must the biceps exert in order for this arm to hold the bowling ball (whose weight is 50. N) steady (i.e. in
equilibrium)? (Assume the bicep exerts a force that is perpendicular to the forearm.)
a.
b.
580 N
220 N
c.
d.
7
18 N
50 N
Name: ________________________
ID: A
____ 24. In this figure, Sue sits on the left, 2 meters from the balance point. Sue has a mass of 50 kg. If Joe (on the
right) has a mass of 100 kg, what must his distance from the balance point be?
a. 0.5 m
b. 4 m
____ 25. What are the units for moment of inertia?
c.
d.
1m
1.5 m
c. kg m
a. kg m2
b. kg m/s
d. N·m
____ 26. The correct answer to this question is “A.” Bubble “A.”
a. A
c. C
b. B
d. D
8
ID: A
Exam 3--PHYS 101--Fall07
Answer Section
MULTIPLE CHOICE
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