A motor cycle starts from rest and accelerates along a straight path at `2m//s^(2)`. At the starting point of the motor cycle there is a stationary electric siren. How far has the motor cycle gone when the driver hears the frequency of the siren at `94%` of its value when the motor cycle was at rest ? (Speed of sound = 330ms^(-2))`

Options

A. (a) `98m`
B. (b) `147m`
C. ( c ) `196m`
D. (d) `49m`

Answer

A

Explanation

(a)
`v_(m)^(2) - u^(2) = 2as` rArr `v_(m)^(2) = 2 xx 2 xx s` :. `v_(m) = sqrt(2)`
According to Doppler's effect
`0.94v = v[(330 - 2sqrt(s))/(330)]` rArr `s = 98.01m`