question_answer

An engine approaches a hill with a constant speed. When it is a distance of 0.9 km it blows a whistle whose echo is heard by the driver after 5 seconds. If the speed of sound in air is 330 m/s, then the speed of the engine is:                                       [JEE ONLINE 09-04-2013]

A)  32 m/s             

B)  27.5 m/s

C)       60 m/s 

D)       30 m/s

Correct Answer: D

Solution :

(d)

Distance travelled by engine

Distance travelled by sound

Speed of engine