15.20 A train, standing at the outer signal of a railway station blows a whistle of frequency 400 Hz in still air.

(i) What is the frequency of the whistle for a platform observer when the train

(a) Approaches the platform with a speed of 10 m s^–1

(b) Recedes from the platform with a speed of 10 m s^–1?

 

(ii) What is the speed of sound in each case? The speed of sound in still air can be taken as 340 m s^–1.

A set of 16 tuning forks are so arranged that each produce 4 beats with the previous one. If the frequency of last tuning fork is double that of first, the frequency of third tuning fork is

A pipe open at both ends produces a note of fundamental frequency V₁. When the pipe is kept with (1/3)^rd of its length in water, it produces a note of frequency V₂.The value of V₁/ V₂ is

A string of linear density 0.4 kg/m is stretched with force of 1000 N. A transverse wave is set up along it. The speed of the wave is

A particle is executing S.H.M. its potential energy v/s displacement graph is given by

The value of restoring force constant is :-

A heavy rope is suspended from rigid support. A wave pulse is set up at the lower end. Then