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An engine standing at the platform blow...

An engine standing at the platform blows a whistle of frequency 305 Hz. If the velocity of sound be 1220 km/h, the frequency of the whistle as heard by a man running towards the engine with a speed of 20 km/s is

A

300 Hz

B

305 Hz

C

310 Hz

D

325 Hz

Text Solution

Verified by Experts

The correct Answer is:
C
`n = 305 Hz, v = 1220 xx (5)/(18) m//s`
`v_(0) = 20 xx (5)/(18) m//s`
`n' = n [(v + v_(0))/(v)] = 305 [(1220 + 20)/(1220)]`
`= (305 xx 1240)/(1220) = 310 Hz`
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