A car moving at a velocity of 17 ms − 1 towards an approaching bus that blows a horn at a frequency of 640 Hz on a straight track. The frequency of this horn appears to be 680 Hz to the car driver. If

Question

A car moving at a velocity of 17 ms − 1 towards an approaching bus that blows a horn at a frequency of 640 Hz on a straight track. The frequency of this horn appears to be 680 Hz to the car driver. If the velocity of sound in air is 340 ms − 1 , then the velocity of the approaching bus is

TestHub · Accepted Answer

Given, velocity of sound, v = 340 m / s Velocity of listner, v L ​ = 17 m / s Velocity of source = v s ​ Frequency of hom emitted v = 640 Hz The apparent frequency v ′ 680 ​ = v v − v s ​ ( v + v l ​ ) ​ = 640 ( 340 − v s ​ 340 + 17 ​ ) ​ On solving we get v s ​ = 4 m / s

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