Sound Connections

Homework and Review Questions

Question #1

• Through which medium does sound travel the fastest? Explain your answer

a. Gasb.Liquidc. solid

Question #2

Lightning strikes 2.5 miles away on a hot (30°C) summer night. How long will it take for the sound of thunder to reach your ears?

Question #3

A train at rest emits a sound at a frequency of 1000 Hz. An observer in a car travels away from the sound source at a speed of 30 m/s. What is the frequency heard by the observer? Assume temperature of air is 20°C

Question #4

• An airplane traveling with half the speed of sound (v = 172 m/s) emits a sound of frequency 5.0 kHz. At what frequency does a stationary listener hear the sound (a) as the plane approaches? (b) after it passes?

Question #5

• Two trains on separate tracks move towards each other. Train A has a speed of 130 km/h and Train B has a speed of 90 km/h. Train B blows its horn, emitting a frequency of 500 Hz. What is the frequency heard by the engineer on train A?

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Question #6

• A supersonic jet breaks the sound barrier while it is 7,000 m directly over you. How much time will it take the sonic boom to reach your ears it sound moves at 345 m/s? How fast is a plane traveling if it moves at Mach 3?

Question #7

a. List 5 different examples of interactions where the pitch changed significantly between two objects as one or both moved towards each other.

b. What characteristics do the examples have in common?

Question #8

explain why the sound changes when the source of object moves past the observer (detector)

Question #9

• The engine of a motorcycle hums at 85 Hz. If the motorcycle travels toward a resting observer at 29.6 m/s, what frequency does the observer hear? Use 343 m/s as the speed of sound.

Question #10

• A submarine is traveling toward a stationary detector. If the submarine emits a 260 Hz sound that is received by the detector as a 262 Hz sound, how fast is the submarine traveling? Use 1533 m/s for the speed of sound in seawater

4 Bonus points• Send me a copy of a short cell phone video of a good

real life example of the Doppler effect

• Want both sound and video.

Send it to me by attachment to an emailin email, tell me the software used to produce

the video

Or post it google, youtube video and email me directions on how to view it