Physics 115 Acoustics
1.
Homework Set #1
Prof. Menningen
p. 1 of 3
Convert the time of 23800000 µs (microseconds) into seconds.
1 10 6 s
23,800,000 μs 
 23.8 s
1 μs
2.
Convert 5.9×105 meters into kilometers: 5.9×10[__] km
(That is, answer the question by giving the correct exponent for the scientific notation expression of the distance in
kilometers.)
5.9  105 m 
1 km
 5.9  102 km  590 km
1000 m
3.
If the frequency of an oscillation is doubled, what happens to its period?
a. It is cut in half.
1
b. It does not change.
T
c. It is doubled.
f
d. It is increased by a factor of 4.
4.
The concert A string on a violin oscillates 440 times per second. If we increase the frequency of
these oscillations, the period will ______.
a. increase
1
b. decrease
T
f
c. stay the same
5.
If t = 75 ms in the figure above, then what is the frequency of the oscillation?
T
6.
A person in a rocking chair completes 8 cycles in 24 s. What is the period of the rocking motion?
f 
7.
75 ms
1s
1
1

 0.01875 s  f  
 53.3 Hz
4 cycles 1000 ms
T 0.01875 s
8 cycles
1
1
 0.333 Hz  T  
 3.00 s
24 s
f 0.333 Hz
A sound wave has a period of 6.8×10−4 s. What is the frequency of the wave?
f 
1
1

 1470 Hz
T 6.8  10 4 s
Physics 115 Acoustics
Homework Set #1
Prof. Menningen
p. 2 of 3
8.
Which of the following is NOT a characteristic of a restoring force that leads to simple harmonic
motion?
a. The restoring force is zero at the equilibrium position.
b. The restoring force obeys Hooke's law.
c. The restoring force always points in the same direction.
d. The restoring force is proportional to the distance from the equilibrium position.
9.
A plot of force versus stretch distance for a given spring is
presented at right. What is the spring constant of this spring?
a. 5.0 N/m
F
5N
b. 20 N/m
F  k x  k  
 20 N/m
c. 0.20 N/m
x 0.25 m
d. 50 N/m
10. What is the phase of the oscillation at point b in the figure above?
a. 95°
b. 315°
c. 215°
d. 135°
11. Is the angular speed of the hour hand of a clock greater than, less than, or equal to the angular speed
of the minute hand?
a. greater than
b. less than
c. equal to
12. Through how many degrees does the minute hand of a clock rotate in 40.0 min?
 360 
  40.0 min   240
 60 min 
 t  
13. The position of an object undergoing simple harmonic motion is given by x = A cos(Bt). What is
the physical significance of the constants A and B?
a. A is the energy stored in the oscillator and B is the frequency of its motion.
b. A is the frequency of the oscillation and B is the period.
c. A is the amplitude of the oscillation and B is the angular speed.
d. A is the amplitude of the oscillation and B is the period of its motion.
14. A plot of force versus stretch distance for a given spring is presented above. What is the period of
oscillation when a 0.31-kg mass is attached to this spring?
T  2
m
0.31 kg
 2
 0.782 s
k
20 N/m
15. If the mass attached to a spring is increased, does the frequency of the mass–spring system increase,
decrease, or stay the same?
a. increase
b. decrease
c. stay the same
T  2
m
k
f 
1
1

T 2
k
m
Physics 115 Acoustics
Homework Set #1
Prof. Menningen
p. 3 of 3
16. The acceleration due to gravity is greater at location A than at location B. If identical pendulums are
taken to both locations, is the period of the pendulum at location A greater than, less than, or equal
to the period of the pendulum at location B?
L
T  2
a. greater than
b. less than
c. equal to
g
17. A simple pendulum makes 5.0 complete swings in 42 s. If the acceleration due to gravity is
9.78 m/s2 at the location of the pendulum, what is the length of the
pendulum in meters?
T
42 s
 8.40 s
5 swings
T  2
L
g
 T 2  4 2
L
g
9.78 m/s  8.40 s   17.5 m
gT 2

L

4 2
4 2
2
2
18. Referring to the figure at right, is the gravitational potential energy of
the bob at point C greater than, less than, or equal to the gravitational
potential energy at point A?
a. greater than
b. less than
c. equal to
19. An object oscillates with no friction or air resistance. Initially, its kinetic energy is 10 J, and its
gravitational potential energy is 90 J. What is the greatest kinetic energy possible for this object?
KEmax  E at the equilibrium point
E  KE  PE  10 J  90 J  100 J the sum of the energies is the total energy
20. The amplitude of an oscillator is cut in half, what happens to the energy stored by the oscillator?
a. It is cut to one-sixteenth.
2
2
2
b. It is cut to a fourth.
 Anew   12 Aold  1
Enew 12 k Anew
c. It is doubled.
 1

 
 
2
Eold
d. It is cut in half.
 Aold   Aold  4
2 k Aold