A police car moving at 30 m s - 1 , chases a motorcyclist. The policeman sounds his horn at 180 Hz , while both of them move towards a stationary siren of frequency 160 Hz . Calculate the speed of the

Question

A police car moving at 30 m s - 1 , chases a motorcyclist. The policeman sounds his horn at 180 Hz , while both of them move towards a stationary siren of frequency 160 Hz . Calculate the speed of the motorcyclist, if it is given that he does not observes any beats (take, the speed of sound = 330 m s - 1 ).

TestHub · Accepted Answer

Speed of sound v S = 330 m s - 1 Case (i), f 1 = f 0 V s - u 0 V s - u s = f 0 330 - u 330 - 30 = 180 ( 330 - u ) 300 f 1 = 180 330 - u 300 ... (i) Case (ii), f 2 = 160 330 + u 330 ... (ii) ∵ There is no beats ∴ f 1 = f 2 180 = 330 - u 300 = 160 330 + u 330 ⇒ 9 330 - u 30 = 8 330 - u 33 ⟹ 9 10 330 - u = 8 11 330 + u ⟹ 32670 - 99 u = 26400 + 80 u ∴ u = 6270 179 = 35.02 m s - 1

Physics - Sound Wave Question with Solution | TestHub

Options:

Doubts & Discussion