Question 1

A pulse is described by  in SI units. What is the velocity of the pulse?

Accepted Answer

A)  3 m/s in the +x direction 
B)  2 m/s in the −x direction 
C)  2 m/s in the +x direction 
D)  4 m/s in the −x direction 
E)  4 m/s in the +x direction

Question 2

Determine the intensity (in W/m2) of a harmonic longitudinal wave with a pressure amplitude of 8.0 × 10−3 N/m2 propagating down a tube filled with helium. (ρ = 0.179 kg/m3, v = 972 m/s.)

Accepted Answer

A)  3.7 × 10−7 
B)  1.8 × 10−7 
C)  9.2 × 10−8 
D)  4.6 × 10−8 
E)  1.5 × 10−9

Question 3

A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction. If the frequency of the siren relative to the police car is 500 Hz, what is the frequency heard by an observer in the truck as the police car approaches the truck? (The speed of sound in air is 343 m/s.)

Accepted Answer

A)  396 
B)  636 
C)  361 
D)  393 
E)  617

Question 4

If y = 0.02 sin (30x − 400t) (SI units), the frequency of the wave is

Accepted Answer

A)  30 Hz 
B)  15/π Hz 
C)  200/π Hz 
D)  400 Hz 
E)  800π Hz

Question 5

The variation in the pressure of helium gas, measured from its equilibrium value, is given by ΔP = 2.9 × 10−5 cos (6.20x − 3 000t) where x and t have units m and s. Determine the speed (in m/s) of the wave.

Accepted Answer

A)  1 515 
B)  153 
C)  484 
D)  828 
E)  101

Question 6

A wave generated in a medium is a longitudinal wave when

Accepted Answer

A)  there is a net transport of matter by the wave. 
B)  the molecules of the medium are unable to exert forces on each other. 
C)  molecular displacements are parallel to the wave velocity. 
D)  molecular displacements are perpendicular to the wave velocity. 
E)  the density of the medium is less than the density of water.

Question 7

By what factor will an intensity change when the corresponding sound level increases by 3 dB?

Accepted Answer

A)  3 
B)  0.5 
C)  2 
D)  4 
E)  0.3

Question 8

Bats can detect small objects such as insects that are of a size on the order of a wavelength. If bats emit a chirp at a frequency of 60 kHz and the speed of soundwaves in air is 330 m/s, what is the smallest size insect they can detect?

Accepted Answer

A)  1.5 mm 
B)  3.5 mm 
C)  5.5 mm 
D)  7.5 mm 
E)  9.8 mm

Question 9

Exhibit 16-1
The figure below shows a sine wave at one point of a string as a function of time.  Use the exhibit to answer the following question(s).
-Refer to Exhibit 16-1. Which of the graphs below shows a wave where the amplitude and the frequency are doubled?

Accepted Answer

A) 
 
B) 
 
C) 
 
D) 
 
E)

Question 10

A point source emits sound waves with a power output of 100 watts. What is the sound level (in dB) at a distance of 10 m?

Accepted Answer

A)  139 
B)  119 
C)  129 
D)  109 
E)  10

Question 11

Calculate the displacement amplitude (in m) of a 20 kHz sound wave in helium if it has a pressure amplitude of 8.0 × 10−3 N/m2. (ρ = 0.179 kg/m3, v = 972 m/s.)

Accepted Answer

A)  2.9 × 10−10 
B)  3.7 × 10−10 
C)  7.8 × 10−9 
D)  2.4 × 10−9 
E)  1.9 × 10−10

Question 12

The variation in the pressure of helium gas, measured from its equilibrium value, is given by ΔP = 2.9 × 10−5 cos (6.20x − 3 000t) where x and t have units m and s, and ΔP is measured in N/m2. Determine the frequency (in Hz) of the wave.

Accepted Answer

A)  1 500 
B)  477 
C)  1.01 
D)  0.32 
E)  239

Question 13

A piano string of density 0.005 0 kg/m is under a tension of 1 350 N. Find the velocity with which a wave travels on the string.

Accepted Answer

A)  260 m/s 
B)  520 m/s 
C)  1 040 m/s 
D)  2 080 m/s 
E)  4 160 m/s

Question 14

Ocean waves with a wavelength of 120 m are coming in at a rate of 8 per minute. What is their speed?

Accepted Answer

A)  8.0 m/s 
B)  16 m/s 
C)  24 m/s 
D)  30 m/s 
E)  4.0 m/s

Question 15

Find the period of a wave of 100-m wavelength in deep water where  .

Accepted Answer

A)  5.0 s 
B)  8.0 s 
C)  12.5 s 
D)  15 s 
E)  0.125 s

Question 16

A person standing in the street is unaware of a bird dropping that is falling from a point directly above him with increasing velocity. If the dropping were producing sound of a fixed frequency, as it approaches the person would hear the sound

Accepted Answer

A)  drop in frequency. 
B)  stay at the same frequency. 
C)  increase in frequency. 
D)  decrease in loudness. 
E)  stay at the same loudness.

Question 17

If the breakers at a beach are separated by 5.0 m and hit shore with a frequency of 0.20 Hz, with what speed are they traveling?

Accepted Answer

The answer of If the breakers at a beach are...

Question 18

For the transverse wave described by  , determine the maximum transverse speed of the particles of the medium.

Accepted Answer

A)  0.192 m/s 
B)  0.6π m/s 
C)  9.6 m/s 
D)  4 m/s 
E)  2 m/s

Question 19

A car approaches a stationary police car at 36 m/s. The frequency of the siren (relative to the police car) is 500 Hz. What is the frequency (in Hz) heard by an observer in the moving car as he approaches the police car? (Assume the velocity of sound in air is 343 m/s.)

Accepted Answer

A)  220 
B)  448 
C)  526 
D)  552 
E)  383

Question 20

While you are sounding a tone on a toy whistle, you notice a friend running toward you. If you want her to hear the same frequency that you hear even though she is approaching, you must

Accepted Answer

A)  stay put. 
B)  run towards her at the same speed. 
C)  run away from her at the same speed. 
D)  stay put and play a note of higher frequency. 
E)  run towards her and play a note of higher frequency.

Exam 16: Wave Motion

A pulse is described by in SI units. What is the velocity of the pulse?

Determine the intensity (in W/m²) of a harmonic longitudinal wave with a pressure amplitude of 8.0 × 10−³ N/m² propagating down a tube filled with helium. (ρ = 0.179 kg/m³, v = 972 m/s.)

A truck moving at 36 m/s passes a police car moving at 45 m/s in the opposite direction. If the frequency of the siren relative to the police car is 500 Hz, what is the frequency heard by an observer in the truck as the police car approaches the truck? (The speed of sound in air is 343 m/s.)

If y = 0.02 sin (30x − 400t) (SI units) , the frequency of the wave is

The variation in the pressure of helium gas, measured from its equilibrium value, is given by ΔP = 2.9 × 10−⁵ cos (6.20x − 3 000t) where x and t have units m and s. Determine the speed (in m/s) of the wave.

A wave generated in a medium is a longitudinal wave when

By what factor will an intensity change when the corresponding sound level increases by 3 dB?

Bats can detect small objects such as insects that are of a size on the order of a wavelength. If bats emit a chirp at a frequency of 60 kHz and the speed of soundwaves in air is 330 m/s, what is the smallest size insect they can detect?

Exhibit 16-1 The figure below shows a sine wave at one point of a string as a function of time. Use the exhibit to answer the following question(s) . -Refer to Exhibit 16-1. Which of the graphs below shows a wave where the amplitude and the frequency are doubled?

A point source emits sound waves with a power output of 100 watts. What is the sound level (in dB) at a distance of 10 m?

Calculate the displacement amplitude (in m) of a 20 kHz sound wave in helium if it has a pressure amplitude of 8.0 × 10−³ N/m². (ρ = 0.179 kg/m³, v = 972 m/s.)

The variation in the pressure of helium gas, measured from its equilibrium value, is given by ΔP = 2.9 × 10−⁵ cos (6.20x − 3 000t) where x and t have units m and s, and ΔP is measured in N/m². Determine the frequency (in Hz) of the wave.