Sample Final Exam #2

1. You need to load a crate of mass m onto the bed of a truck. One possibility is just to lift the crate
straight up over a height h, equal to height of the truck's bed. The force exert in this case is F1
and the work done in this case is W1. The other possibility is to slide the crate up the frictionless
ramp of length L as shown in the figure. In this case you exert force F2 and perform work W2.
Which statement is true?
A.
B.
C.
D.
E.
F1 > F2 and W1 > W2
F1 =F2 and W1 > W2
F1 = F2 and W1 = W2
F1 > F2 and W1 < W2
F1 > F2 and W1 = W2
2. The human ear canal is much like an organ pipe that is closed at one end (at the tympanic
membrane, or eardrum) and open at the other. Suppose that a person's ear canal is of length
L = 0.0277 m. What is the fundamental frequency of the ear canal if the speed of sound is 343
m/s?
A.
B.
C.
D.
E.
1.3 kHz
3.8 kHz
1.8 kHz
3.1 kHz
2.8 kHz
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3. The diagram shows a cube floating in a container of oil. If D=20.0 cm, what is the density of the
cube if d= 5cm?
 oil  0.9 cmg  900 mkg
3
3
d
D
A.
B.
C.
D.
E.
1125 kg/m3
675 kg/m3
1575 kg/m3
450 kg/m3
225 kg/m3
4. If you drop an object from a height h above the ground, how long would it take for the object to
reach a speed of 39 m/s assuming that the object is initially high enough that it doesn't hit the
ground first (neglect air resistance)?
A.
B.
C.
D.
E.
1.4 s
4.0 s
2.0 s
1.0 s
3.0 s
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5. A block is connected to a spring and hung vertically. The block is set into motion and a short time
later, a sequence of nine snapshots is recorded (the photos are taken at regular time intervals).
These snapshots are arranged side-by-side below.
t=0
t=1
t=2
t=3
t=4
t=5
t=6
t=7
t=8
Of the choices below, at what instant in time is the block experiencing the largest magnitude of
the velocity?
A.
B.
C.
D.
E.
t=2
t=3
t=4
t=6
t=7
6. A violinist plays the note 'A' (frequency 440 Hz). This is the fundamental frequency for the string.
If the string is 15 cm long, what is the wave speed on the string?
A.
B.
C.
D.
E.
132 m/s
264 m/s
66 m/s
343 m/s
We cannot determine this without knowing the tension on the string and its linear mass
density.
7. A ball of mass 0.5 kg is dropped from rest at a point some distance above the ground. If the ball's
kinetic energy just before it hits the ground is 25 J, from what height was the ball dropped?
(Use g = 10 m/s2)
A.
B.
C.
D.
E.
1.0 m
50.0 m
5.0 m
0.5 m
4.0 m
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8. A student swings a 0.25 kg mass around in a vertical circle using a string of length 0.5 m. The
rock is swinging at a constant speed of 4 m/s. What was the tension in the string when the mass is
at the top of the swing?
A.
B.
C.
D.
E.
9.
5.5
9.8
10.5
8
2.5
Three blocks of the same size and shape are
placed in a tank of water. The masses of the
blocks are unknown. Blocks 1 and 2 are
suspended from strings attached to spring scales.
Both spring scales read 5 N. Block 3 is floating
as shown.
3
1
Rank the magnitudes of the buoyant forces on
each of the blocks, from least to greatest.
A.
B.
C.
D.
E.
2
3<1<2
2<1<3
1=2<3
3<1=2
1=2=3
10. Two acrobats flying through the air grab and hold onto each other in midair as part of a circus act.
One acrobat has a mass of 60 kg and has a horizontal velocity of 5 m/s just before the grab.
Another acrobat has a mass of 50 kg and has a horizontal velocity of -3 m/s just before the grab.
Their horizontal velocity immediately after they grab onto each other is:
A. 0.6 m/s
D. 2.0 m/s
B. 4.1 m/s
E. 1.4 m/s
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C. 3.0 m/s
11. A block of mass 4.0 kg lies on a frictionless horizontal table in contact with a 6.0 kg block. At the
opposite side of the 4.0 kg block, a constant horizontal force of 100.0 N is applied as shown in
the diagram. What is the magnitude of the horizontal force on the 6.0 kg block?
A.
B.
C.
D.
E.
150 N
60 N
0N
40 N
100 N
12. The displacement of a wave traveling in the positive x-direction is
y(x, t) = (7.5 cm)cos(5.7x -75t), where x is in meters and t is in seconds.
What is the speed of this wave?
A.
B.
C.
D.
E.
526.5 m/s
42.75 m/s
427.5 m/s
13.1 m/s
0.076 m/s
13. Two children are riding on a merry-go-round. Child A is at a greater distance from the axis of
rotation than child B. Which child has the larger angular speed?
A.
B.
C.
D.
E.
child A
In order to find the speed we need to know the radii.
child B
In order to find the speed we need to know the masses.
They have the same angular speed.
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14. Identical forces act for the same length of time on two different masses. The change in momentum
of the smaller mass is
A.
B.
C.
D.
E.
equal to the change in momentum of the larger mass.
larger than the change in momentum of the larger mass.
smaller than the change in momentum of the larger mass, but not zero kg m/s.
cannot tell without knowing the masses.
zero kg m/s.
15. Two carts on a frictionless track are launched toward each other. Cart A, on the left, has a mass
of 2.00 kg and cart B, on the right, has a mass of 1.5 kg. After the collision, it is observed that
cart A is moving to the right at a speed of 2 m/s and cart B is also moving to the right at a speed
of 3 m/s. How fast was cart A traveling before the collision if cart B was initially moving towrds it
with a speed of 1.5 m/s?
VAi=? Before: VBi= ‐1.5 m/s mA=2 kg MB=1.5 kg VAf=2 m/s After: A.
B.
C.
D.
E.
VBf=3 m/s mA=2 kg MB=1.5 kg 6.50 m/s
3.50 m/s
5.38 m/s
3.13 m/s
The scenario described is physically impossible. There's no way that cart A could keep
moving to the right after the collision.
16. A soccer ball is kicked with a speed of 20 m/s at an angle of 35 degrees above the horizontal.
How long is the ball in the air?
A.
B.
C.
D.
E.
2.9 s
1.2 s
3.3 s
2.3 s
4.1 s
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17. You are doing a front kick. At a given instant, your leg (mass of 10 kg, L = 1.1 m) is straight and
horizontal, as shown below. What is the magnitude of the torque about the hip joint on your leg
due to gravity at this instant? (Assume your leg is uniform.)
A.
B.
C.
D.
E.
54 Nm
98 Nm
108 Nm
11 Nm
0 Nm
18. What spring constant k would you need to have a 3 kg mass oscillate on the spring with the same
period T as the mass would have hanging from a simple pendulum of length 0.5 meters?
A.
B.
C.
D.
E.
13 N/m
59 N/m
0.15 N/m
6 N/m
177 N/m
19. You observe a 10 kg object moving to the left with a constant velocity of 5 m/s for two seconds.
The net force acting on the object during this time must have been:
A.
B.
C.
D.
E.
50 N
0N
25 N
-50 N
-25 N
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20. A roller coaster of mass 420 kg is moving with a speed of 10.0 m/s at position A as shown. The
vertical height at position A above ground level is 200 m and at position C is 160 m. Assume
friction is negligible. The speed of the roller coaster at point C is approximately
A.
B.
C.
D.
E.
56 m/s
30 m/s
63 m/s
59 m/s
28 m/s
21. A student is in possession of three tunuing forks each labeled with their respective frequencies
(354 Hz, 365, and 382 Hz). If all three tuning forks are struck at the same instant the student will
be able to hear the following number of beats per second:
A.
B.
C.
D.
E.
17
11, 17, and 28
747 and 736
11
719 and 736
22. An inelastic collision between two objects is characterized by the following
A.
B.
C.
D.
E.
Total energy of the system is conserved
Total kinetic energy of the system remains constant
Total momentum of the system is conserved
Both A and B are true
Both A and C are true
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23. A person was pushing a box up an incline (as shown below). As the person pushes, which of the
free body diagrams provided best describes the forces acting on the box?
A. B.
FN FN FPush FPush fK fK W W C. D.
FN FN FPush FPush fK fK W W Page 9