AP Physics Homework – Waves!
Name:
1) A radar gun is often used to measure the speed of a major league pitch by reflecting a pulse of radio waves off of
a moving ball. Describe how the Doppler effect can give the speed of the ball from a measurement of the
frequency of the reflected beam.
2) Is the beat frequency produced when a 245 Hz tone and a 240 Hz tone are played together greater than, less than
or equal to the beat frequency produced when a 140 Hz tone and a 145 Hz tone are played together? Explain.
3) You stand near the tracks as a train approaches with constant speed. The train is operating its horn continuously,
and you listen carefully to the sound that it makes. For each of the following properties of the sound, state
whether it increases, decreases or stays the same as the train gets closer.
a) Sound Intensity
b) Frequency
c) Wavelength
d) Speed
4) A person is walking away from a stationary sound source. Indicate whether the person will hear a higher or lower
frequency than is emitted, and explain why.
5) An ambulance is moving toward an observer, emitting a constant sound frequency. Indicate whether the person
will hear a higher or lower frequency than is emitted, and explain why.
6) A small vibrating object S moves across the surface of a ripple
tank producing the wave fronts shown to the right. The wave fronts
move with speed v. The object is traveling in what direction and
with what speed relative to the speed of the wave fronts produced?
(A)
(B)
(C)
(D)
(E)
Direction
Speed
To the right
To the right
To the right
To the left
To the left
Equal to v
Less than v
Greater than v
Less than v
Greater than v
7) A vibrating tuning fork sends sound waves into the air surrounding
it. During the time in which the tuning fork makes one complete
vibration, the emitted wave travels
(A)
(B)
(C)
(D)
(E)
one wavelength
about 340 meters
a distance directly proportional to the frequency of the vibration
a distance directly proportional to the square root of the air density
a distance inversely proportional to the square root of the pressure
8) In the Doppler effect for sound waves, factors that affect the
frequency that the observer hears include which of the following?
I. The speed of the source
II. The speed of the observer
III. The loudness of the sound
(A) I only
(B) III only
(D) II and III only
(C) I and II only
(E) I, II, and III
9) Two fire trucks have sirens that emit waves of the same frequency.
As the fire trucks approach a person, the person hears a higher
frequency from truck X than from truck Y. Which of the following
statements about truck X can be correctly inferred from this
information?
I. It is traveling faster than truck Y.
II. It is closer to the person than truck Y.
III. It is speeding up and truck Y is slowing down.
(A) I only
(B) III only
(D) II and III only
(C) I and II only
(E) I, II, and III
10) A small vibrating object on the surface of a ripple tank is the
source of waves of frequency 20 Hz and speed 60 cm/s. If the
source S is moving to the right, as shown above, with speed 20
cm/s, at which of the labeled points will the frequency measured
by a stationary observer be greatest?
(A) A
(B) B
(C) C
(D) D
(E) It will be the same at all four points.