Name: ________________________
Exam 3--PHYS 101--F15
Multiple Choice
Identify the choice that best completes the statement or answers the question.
4. Consider the figure in problem #2. A cart starts at
point A with a speed of 4 m/s. Which of the
following statements best describes the cart’s
energy at point (d). (Let the ground be h=0.)
1. It takes 100 m to stop a car initially moving at
25.0 m/s. The distance required to stop the
same car moving at 50.0 m/s under the same
conditions is
a. 100 m.
b. 25.0 m.
c. 50.0 m.
d. 200 m.
e. 400 m.
a.
b.
c.
d.
e.
2. Consider this figure. A cart starts at point A with a
speed of 4 m/s. What is the speed of the cart at
point b?
5. By what factor does the kinetic energy of a car
change if its velocity is doubled?
a.
b.
c.
d.
e.
a.
b.
c.
d.
e.
At point (d), PE=0 and KE=0.
At point (d), PE>0 and KE=0.
At point (d), PE=0 and KE>0.
At point (d), PE>0 and KE>0.
It depends on the mass of the cart.
1
2
4
0.5
0.25
6. Which of these statements is/are true?
I. Conservative forces require contact between 2
objects.
II. Field forces conserve energy.
III. Friction is a conservative force.
IV. Conservative forces are path-dependent.
a. II only
b. I, III, and IV
c. II & IV
d. all are true
15 m/s
220 m/s
4.2 m/s
10. m/s
16 m/s
3. Consider the figure in the previous problem. A cart
starts at point A with a speed of 4 m/s. If the cart
comes to rest at point (e), what is the height at that
point?
7. A 10-kg toy car moving at 5.0 m/s hits an
a.
b.
c.
d.
e.
initially uncompressed horizontal spring with a
spring constant of 2.5 × 102 N/m. Neglecting
the mass of the spring, the maximum
compression of the spring is
a. 1.0 m.
b. 0 m.
c. 0.20 m.
d. 2.0 m.
e. 50 m.
13 m
4.0 m
10. m
9.0 m
11 m
1
11. Consider this perfectly inelastic collision. What is
the magnitude of the final velocity of the two
particles?
8. A 10-kg toy car moving at 5.0 m/s hits an
initially uncompressed horizontal spring with a
spring constant of 2.5 × 102 N/m. Neglecting
the mass of the spring, what is the total elastic
potential energy when the spring is completely
compressed?
a.
b.
c.
d.
e.
200 J
50. J
13,000 J
500 J
130 J
9. A spring has a spring constant of 1200 N/m.
You apply a force of 600. N to compress the
spring. By how much do you compress the
spring?
a. 0.50 m
b. 1.0 m
c. 3.4 m
d. 2.0 m
e. 720,000 m
a.
b.
c.
d.
e.
12 m/s
0.5 m/s
3.3 m/s
0.67 m/s
1.5 m/s
12. An open cart rolls along a frictionless track while it
is raining. As it rolls, what happens to the speed
of the cart as the rain collects in it? (assume that
the rain falls vertically into the box)
10. A machine gun is attached to a railroad flatcar that
rolls with negligible friction. If the railroad car has
a mass of 6.25 × 104 kg, how many bullets of mass
0.025 kg would have to be fired at 250 m/s off the
back to give the railroad car a forward velocity of
0.5 m/s?
a.
b.
c.
d.
speeds up
maintains constant speed
slows down
stops immediately
13. A crane drops a 0.30 kg steel ball onto a steel plate.
The ball's speed just before impact is 4.5 m/s; after
impact, it rebounds at 4.2 m/s. If the ball is in
contact with the plate for 0.030 s, what is the
magnitude of the average force that the ball exerts
on the plate during impact?
a.
b.
c.
d.
3,000
2,000
5,000
400
a.
b.
c.
d.
2
3.5 N
87 N
133 N
3.0 N
14. A 0.10-kg ball is moving at 6 m/s when it is hit by a
bat, causing it to reverse direction and have a speed
of 14 m/s. What is the magnitude of the change in
the momentum of the ball?
a.
b.
c.
d.
17. Which of these bodies has the largest momentum?
(“M” represents mass; “V” represents velocity.)
I. Mass 8M and speed V
II. Mass M and speed 8V
III. Mass 3M and speed 3V
IV. Mass 2M and speed 3V
a. I & II
b. III alone
c. IV alone
d. III & IV
e. II alone
0.60 kg⋅m/s
2.0 kg⋅m/s
200 kg⋅m/s
0.80 kg⋅m/s
18. If the momentum of an object is tripled, its kinetic
energy will change by what factor? (Assume the
mass of the object is unchanged.)
15. 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.
b.
c.
d.
a.
b.
c.
d.
19. Which of these bodies has the largest energy? (“M”
represents mass; “V” represents velocity.)
I. Mass 8M and speed V
II. Mass M and speed 8V
III. Mass 3M and speed 3V
IV. Mass 2M and speed 3V
a. I & II
b. III alone
c. IV alone
d. III & IV
e. II alone
the heavier fragment has a higher velocity than
the light one
the lighter and heavier fragments have the same
momentum (but in opposite directions)
the lighter fragment has more momentum than
the heavy one
the lighter and heavier fragments have the same
velocity (but in opposite directions)
20. 2600 rev/min is equivalent to which of the
following?
a.
b.
c.
d.
16. A force of 100 N acts on a 100 kg boulder for 2
seconds; the same force acts on a 1 kg stone for 2
seconds. Which experiences the larger change in
momentum?
a.
b.
c.
zero
one-third
three
nine
the boulder
the stone
both the same
3
60 rad/s
2600 rad/s
270 rad/s
43 rad/s
21. Between midnight and 3 am, the hour hand of a
clock has what displacement?
a.
−π
2
b.
-45 degrees
c.
d.
e.
π
2
−π
π
24. A Ferris wheel, rotating initially at an angular
speed of 0.500 rad/s, accelerates over a 7.00 s
interval at a rate of 0.0400 rad/s 2. What angular
displacement does the Ferris wheel undergo in this
7.00 s interval?
radians
radians
radians
radians
a.
b.
c.
d.
22. The distance from the center of a Ferris wheel to a
passenger seat is 12 m. What centripetal
acceleration does a passenger experience when the
wheel's angular speed is 0.50 rad/s?
3.00 rad
0.500 rad
2.50 rad
4.48 rad
25. Consider a point on a spinning wheel rotating with
rad
α = 0 2 . Which of these statements best
s
a.
b.
c.
d.
describes the linear velocity of the point?
a. the linear velocity is the same as the angular
velocity
b. the linear velocity does not change
c. the linear velocity is changing constantly
d. the linear velocity equals α
3.0 m/s2
16.9 m/s2
6.0 m/s2
9.0 m/s2
26. An object at rest begins to rotate with a constant
angular acceleration. If this object rotates through
an angle θ in the time t, through what angle did it
rotate in the time 1/2 t?
23. A boy swings a 10.0 kg stone in a horizontal circle
with a radius of 2.0 m. The string breaks under 80.0
N of tension. What is the maximum speed (in m/s)
the stone can have?
a.
b.
a.
b.
c.
d.
16 m/s
4.0 m/s
400 m/s
0.25 m/s
c.
d.
e.
4
4θ
1
θ
2
2θ
1
θ
4
3
θ
4
ID: A
Exam 3--PHYS 101--F15
Answer Section
MULTIPLE CHOICE
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