1 ) At a factory, a noon whistle is sounding with a frequency of 451 Hz. As a ca

Question

1 ) At a factory, a noon whistle is sounding with a frequency of 451 Hz. As a car traveling at 84 km/h approaches the factory, the driver hears the whistle at frequency fi. After driving past the factory, the driver hears frequency ff. What is the change in frequency ff - fi heard by the driver? (Assume a temperature of 20° C.)

2 ) A source of sound waves of frequency 0.9 kHz is traveling through the air at 0.75 times the speed of sound.

(a) What is the frequency of the sound received by a stationary observer if the source moves toward her?

(b) Now, the source moves away from the stationary observer. What is the frequency of the sound received in this case?

Explanation / Answer

1) Frequency of whistle, F = 451 Hz The velocity of whistle source, Vs = 0 The velocity of the driver, Vo = 84 kmph = 23.3 m/s The velocity of sound in air at temparature 20 deg C = 343 m/s The frequency of whistle hear by the driver when he approaches the factory is given by the equation, fi = F[ (V + Vo) / V ] = 481.6 Hz The frequency of whistle hear by the driver when he away from the factory is given by the equation, ff = F[ (V - Vo) / V ] = 420.4 Hz So the difference, ff - fi = 61.2 Hz ACCORDING TO CRAMSTER'S RULE EACH QUESTION MUST BE A SEPARATE POST. IF YOU REPOST THE REMAINING SEPARATELY I WILL ANSWER IT. ACCORDING TO CRAMSTER'S RULE EACH QUESTION MUST BE A SEPARATE POST. IF YOU REPOST THE REMAINING SEPARATELY I WILL ANSWER IT.

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