question_answer

A train is moving with a constant speed along a circular track. The engine of the train emits a sound of frequency F. The frequency heard by the guard at rear end of the train:

A)  is less than f

B)  is greater than f

C)  is equal to f

D)  may be greater than, less than or equal to f depending on the factors like speed of train, length of train and radius of circular track:

Correct Answer: C

Solution :

Let V = speed of sound and u = speed of train Then,      \[{{V}_{S}}={{V}_{0}}=u\] and        \[F=F\left( \frac{V+{{V}_{0}}\,\cos \theta }{V+{{V}_{s}}\,cos\theta } \right)\]             \[=F\,(as\,{{V}_{0}}={{V}_{S}})\]