Question 1

The Young's modulus for aluminum is 7.02 × 1010 N/m2.If the speed of sound in aluminum is measured to be 5.10 km/s,find its density (in kg/m3).

Accepted Answer

A) 11.3 × 103 
B) 7.80 × 103 
C) 2.70 × 103 
D) 29.3 × 103 
E) 1.40 × 103 
A) 11.3 × 103 
B) 7.80 × 103 
C) 2.70 × 103 
D) 29.3 × 103 
E) 1.40 × 103

Question 2

A bat,flying at 5.00 m/s,emits a chirp at 40.0 kHz.If this sound pulse is reflected by a wall,what is the frequency of the echo received by the bat? (vsound = 340 m/s. )

Accepted Answer

Question 3

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

Question 4

Calculate the pressure amplitude (in N/m2)of a 500 Hz sound wave in helium if the displacement amplitude is equal to 5.0 × 10−8 m.(ρ = 0.179 kg/m3,v = 972 m/s. )

Accepted Answer

A) 3.5 × 10−2 
B) 1.6 × 10−2 
C) 2.7 × 10−2 
D) 4.2 × 10−2 
E) 2.0 × 10−2 
A) 3.5 × 10−2 
B) 1.6 × 10−2 
C) 2.7 × 10−2 
D) 4.2 × 10−2 
E) 2.0 × 10−2

Question 5

A friend hands you an equation sheet with the following equation for the Doppler effect:  
)This version of the equation is correct with signs as given only if

Accepted Answer

A) the observer and source are approaching each other. 
B) the observer is approaching the source while the source is moving away from the observer. 
C) the observer is moving away from the source while the source is approaching the observer. 
D) the observer and source are moving away from each other. 
E) the observer and source are moving in perpendicular directions. 
A) the observer and source are approaching each other. 
B) the observer is approaching the source while the source is moving away from the observer. 
C) the observer is moving away from the source while the source is approaching the observer. 
D) the observer and source are moving away from each other. 
E) the observer and source are moving in perpendicular directions.

Question 6

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 
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 7

If a plane is flying at a speed so that the apex half-angle of its shockwave is 30°,what is its speed if the speed of sound is 320 m/s?

Accepted Answer

A) 960 m/s 
B) 640 m/s 
C) 320 m/s 
D) 160 m/s 
E) Choose this answer if a shock wave cannot form in this situation. 
A) 960 m/s 
B) 640 m/s 
C) 320 m/s 
D) 160 m/s 
E) Choose this answer if a shock wave cannot form in this situation.

Question 8

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 is 500 Hz relative to the police car,what is the change in frequency (in Hz)heard by an observer in the truck as the two vehicles pass each other? (The speed of sound in air is 343 m/s. )

Accepted Answer

A) 242 
B) 238 
C) 240 
D) 236 
E) 234 
A) 242 
B) 238 
C) 240 
D) 236 
E) 234

Exam 17: Sound Waves

The Young's modulus for aluminum is 7.02 × 1010 N/m2.If the speed of sound in aluminum is measured to be 5.10 km/s,find its density (in kg/m3).

A bat,flying at 5.00 m/s,emits a chirp at 40.0 kHz.If this sound pulse is reflected by a wall,what is the frequency of the echo received by the bat? (vsound = 340 m/s. )

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. )

Calculate the pressure amplitude (in N/m2)of a 500 Hz sound wave in helium if the displacement amplitude is equal to 5.0 × 10−8 m.(ρ = 0.179 kg/m3,v = 972 m/s. )

A friend hands you an equation sheet with the following equation for the Doppler effect: )This version of the equation is correct with signs as given only if

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. )

If a plane is flying at a speed so that the apex half-angle of its shockwave is 30°,what is its speed if the speed of sound is 320 m/s?

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The Young's modulus for aluminum is 7.02 × 10¹⁰ N/m².If the speed of sound in aluminum is measured to be 5.10 km/s,find its density (in kg/m³).

A bat,flying at 5.00 m/s,emits a chirp at 40.0 kHz.If this sound pulse is reflected by a wall,what is the frequency of the echo received by the bat? (v_sound = 340 m/s. )

Calculate the pressure amplitude (in N/m²)of a 500 Hz sound wave in helium if the displacement amplitude is equal to 5.0 × 10−⁸ m.(ρ = 0.179 kg/m³,v = 972 m/s. )

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. )