1.

A whistle producting sound waves of frequencies 9500 Hz and above is approaching a stationary person with v ms^(-1). The velocity of sound in air is 300 ms^(-1) . If a person can hear frequencies upto 10,000 Hz, the maximum value of v upto which he can hear the whistle is :

Answer»

`15 SQRT(2) ms^(-1) `
`(15)/(sqrt(2)) ms^(-1)`
`15 ms^(-1)`
`30 ms^(-1)`

Solution :APPARENT frequency `v. = ((V)/(V - U_(s)) ) .v`
10,000 = `((300)/(300 - U_(s)) ) . 9500`
`rArr U_(s) = 15 ms^(-1)`.
So correct CHOICE is (C).


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