A boy standing idle sounds a whistle to his friend at a distance of 1200 m moving away from him in a speeding car at 108 kms /hr. Find the duration after which his friend is going to hear him. (Speed of sound = 330m/sec).

a) 3.6 secs b) 4.00 secs c) 40 secs d) None of these

• 4 secs.
  
  b) 4.00 secs
  
  If friend hears sound after t secs, then
  
  330*t = 1200 +(108*5/18)*t
  300t =1200
  t= 4 secs
• 13 years agoHelpfull: Yes(2) No(0)