At each of two stations A and B, a siren is sounding with a constant frequency of 250 cycle `s^-1`. A cyclist from A proceeds straight towards B with a velocity of `12kmh^-1` and hear `5 beats//s`. The velocity of sound is nearly:

Options

A. `328ms^(-1)`
B. `320ms^(-1)`
C. `333ms^(-1)`
D. `336ms^(-1)`

Answer

C

Explanation

If `f_B` is the frequency as heard by cyclist from source B and `f_A` is the frequency as heaed by the cyclist from source A.
Then `f_B-f_A=5`
`250((V_S+(10)/(3))/(V_S))-250((V_S-(10)/(3))/(V_S))=5`
`=333m//s`