Physics 15.73 HELP <span title="PLEASE!!!!!!!!!!!!!!!!!!!!!!!!!!!!">PLEASE!!!!!!!!!!!!!!!!!!!...</span>

Question

A source of sound moves toward you at speed v_s and away from Jane, who is standing on the other side of it. You hear the sound at twice the frequency as Jane.

What is the speed of the source? Assume that the speed of sound is 340 m/s?

Answer 1

Let

v = wave speed (i.e. speed of sound) = 340 m/s

f = actual frequency

f1 = frequency heard by me

f2 = frequency heard by Jane

vs = source speed = ?

Observer&#039;s speed is zero.

Source is moving away from Jane. By Doppler&#039;s law

f2 = f * v/(v + vs) --------------(1)

Source is moving towards me. By Doppler&#039;s law

f1 = f*v/(v - vs)-------------(2)

Dividing (2) by (1),

f1/f2 = (v+vs)/(v-vs)

Given, f1/f2 = 2

Therefore,

(v+vs)/(v-vs) = 2

Or, v + vs = 2v - 2vs

Or, vs + 2vs = 2v - v

Or, 3vs = v

Or, vs = v/3 = 340/3 = 113.33 m/s

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