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Study Guide for PHYS 151 Final Exam
November 29, 2005
Dr. C. Gerousis
Questions 1 – 10 come from section I of Exam 1 and 2 (5 from each exam).
Questions 11 - 20 are chosen from the following:
Part I. Choose the one alternative that best completes the statement or answers the
question. Use g = 9.81 m/s2 where necessary.
1. In a typical golf swing, the club is in contact with the ball for about 0.0012 s. If
the 45 g ball acquires a speed of 62 m/s, estimate the magnitude of the force
exerted by the club on the ball.
[2.33] kN
2. Two ice skaters stand at rest in the center of an ice rink. When they push off
against one another the 45 kg skater acquires a speed of 0.71 m/s. If the speed of
the other skater is 0.87 m/s, what is this skater's mass?
[36.7] kg
3. A honeybee with a mass of 0.175 g lands on one end of a popsicle stick. After
sitting at rest for a moment, the bee runs toward the other end with a velocity 1.55
cm/s relative to the still water. What is the speed of the 4.65 g stick relative to the
water? (Assume the bee's motion is in the negative direction.)
[0.583] mm/s
4. A 1.43 kg bowling trophy is held at arm's length, a distance of 0.505 m from the
shoulder joint.
(a) What torque does the trophy exert about the shoulder if the arm is horizontal?
[7.08] N m
(b) What torque does the trophy exert about the shoulder if the arm is at an
angle of 19.0° below the horizontal? [6.7] N m
5. A torque of 1.01 N m is applied to a bicycle wheel of radius 31 cm and mass
0.71 kg. Treating the wheel as a hoop, find its angular acceleration. [14.8] rad/s2
6. A 0.013 kg record with a radius of 15 cm rotates with an angular speed of 34 rpm.
Find the angular momentum of the record. [0.000521] kg m2/s
7. At Zion National Park a loud shout produces an echo 1.5 s later from a colorful
sandstone cliff. How far away is the cliff? [257] m
8. A sound wave in air has a frequency of 430.0 Hz.
(a) What is its wavelength? [0.798] m
(b) Calculate the wavelength for a sound wave with a frequency of 460.0 Hz.
[0.746] m
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9. The intensity level in a truck is 95.0 dB. What is the intensity of this sound?
[3.16] mW/m2
10. The organ pipe in the figure is 3.3 m long.
(a) What is the frequency of the standing wave shown in the pipe? [78] Hz
(b) What is the fundamental frequency of this pipe? [26] Hz
11. The frequency of the standing wave shown in the figure is 247 Hz.
(a) What is the fundamental frequency of this pipe? [124] Hz
(b) What is the length of the pipe? [1.39] m
12. A glass window 0.60 cm thick measures 79 cm by 42 cm. How fast does heat
flow through this window if the inside and outside temperatures differ by 18°C?
[50.2] kJ/min
13. A steel suspension-bridge is 3910 m long. How much longer is the bridge on a
warm summer day (31.0°C) than on a cold winter day (-5.00°C)? [1.69] m
14. During a workout, a person repeatedly lifts a 14 lb barbell through a distance of
1.5 ft. How many "reps" of this lift are required to burn off 120 Cal? [17600]
15. A person slowly lowers a 3.7 kg crab trap over the side of a dock, as shown in the
figure. What torque does the trap exert about the person's shoulder? [25.4] N · m
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Questions 21 – 30 are conceptual questions that are selected from the lecture notes of
chapters 11, 12, 14, and 16. See www.pcs.cnu.edu/~gerousis/phys151
Example1
In an elastic collision,
(a) Only momentum is conserved
(b) Only kinetic energy is conserved
(c) Both, momentum and kinetic energy are conserved
Example 2
In a hot oven the air and the metal rack are at the same temperature, but the metal
rack feels hotter because
(a) The metal is denser than air
(b) T for the hand and metal is larger than T for hand and air.
(c) The air has lower thermal conductivity than the metal
Example 3
A satellite is orbiting the Earth as shown below. At what part of the orbit, if any, is
the kinetic energy largest?
(a) A
(b) B
(c) A and B
A
B
Example 4
A light is a
(a) transverse wave
(b) longitudinal wave
(c) Both (a) and (b)
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Part II.
Two problems are taken from exam 1 and 2 (one problem from each exam). In addition,
I will pick 5 from the following problems:
1. Two A person holds a 1.42 N baseball in his hand, a distance of 2L = 34.0 cm from the
elbow joint, as shown in the figure. The biceps, attached at a distance of d = 3.23 cm
from the elbow, exert an upward force of 13.2 N on the forearm. Consider the forearm
and hand to be a uniform rod with a mass of 1.04 kg.
(a) Calculate the magnitude of the net torque acting on the forearm and hand. Use the
elbow joint as the axis of rotation. [1.79] N m
(b) If the net torque obtained in part (a) is nonzero, in which direction will the forearm
and hand rotate? [clockwise]
(c) Would the net torque exerted on the forearm and hand? Why?
2. The collision between a hammer and a nail can be considered to be approximately
elastic. Estimate the kinetic energy acquired by a 10 g nail when it is struck by a 550 g
hammer moving with a speed of 3.4 m/s. [0.223] J
3. A typical GPS (Global Positioning System) satellite orbits at an altitude of 2.0 107
m. (Astronomical data needed for this problem can be found on the inside back cover of
the text.)
(a) Find the orbital period of such a satellite. [11.8] hours
(b) Find the orbital speed of such a satellite. [3.89] km/s
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4. When the Earth, Moon, and Sun form a right triangle with the Earth located at the
right angle, as shown in Figure 12-22, the Moon is approaching its third quarter. (The
Earth is viewed here from above its north pole.) Find the magnitude and direction of the
net force exerted on the Earth.
[3.54e+22] N
[0.321]° clockwise from the ray from earth to sun
5. A car with a mass of 950 kg and an initial speed of v1 = 17.8 m/s approaches an
intersection, as shown in the figure. A 1300 kg minivan traveling northward is heading
for the same intersection. The car and minivan collide and stick together. If the direction
of the wreckage after the collision is 37.0° above the x axis, what is the initial speed of
the minivan and the final speed of the wreckage?
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6. A train on one track moves in the same direction as a second train on the adjacent
track. The first train, which is ahead of the second train and moves with a speed of 30
m/s, blows a horn whose frequency is 125 Hz. If the frequency heard on the second train
is 128 Hz, what is its speed? (Express your answer to the nearest 0.1 m/s.) [39] m/s
Note that the directions could vary on the final exam.
7. A ceramic coffee cup with m = 131 g and c = 1090 J/(kg K), is initially at room
temperature (24.0°C). If 185 g of 80.3°C coffee and 12.2 g of 5.00°C cream are added to
the cup, what is the equilibrium temperature of the system? Assume that no heat is
exchanged with the surroundings, and that the specific heat of coffee and cream are the
same as the specific heat of water. [68]°C
8. When a ceiling fan rotating with an angular speed of 2.30 rad/s is turned off, a
frictional torque of 0.196 N m slows it to a stop in 4.20 s. What is the moment of inertia
of the fan? [0.358] kg m2
9. A string is fixed at one end, passes over a massless pulley, and is attached to a 5-g
hanging mass. The mass of 1 m of the string is 2 g. If a 10 Hz wave of amplitude 5 cm
passes along the string, (a) what is its wavelength? [0.49 m] (b) How long does it take to
travel a distance of 1 m from point A to B? [0.2 s]
A
B
m
10. A guitar string 60 cm long vibrates with a standing wave that has three antinodes. (a)
Which harmonic is this? (b) What is the wavelength of this wave? (c) If this harmonic is
excited with a frequency of 600 Hz, what is the frequency of the fundamental?
(a) 3 (b) 0.4 m (c) f1 = 200 Hz
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