Question

A girl stands 160 m away from a high wall and claps her hands at a steady rate so that each clap coincides with the echo of the one before. If her clapping rate is 60 per minute, what value does this give for the speed of sound?


b. If she moves 40 m closer to the wall she finds the clapping rate has to be 80 per minute. What value do these measurements give for the speed of sound?

c. If she moves again and finds the clapping rate becomes 30 per minute, how far is she from the wall if the speed of sound is the value you found in a?

Answer 1

Step 1

Part (a): Distance between the girl and the wall = 160 m

Frequency of the clap = 60/60 = 1HZ

Step 2

Wavelength of the clap = (distance covered by sound to going to wall + distance covered by sound to coming back from the wall)

λ = 2 X 160 = 320 m

Speed of sound can be calculated as:

Physics homework question answer, step 2, image 1

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Step 3

Part (b): Distance between the girl and the wall = 160 – 40 =120 m

Wavelength = ...

Physics homework question answer, step 3, image 1