Question

A sonometer wire under tension of 64 Newton vibrating in its fundamental mode is in resonance with a vibrating tuning fork. The vibrating portion of the sonometer wire has a length of 10 cm and a mass of one gm. The vibrating tuning fork is now moved away from the vibrating wire with a constant speed and an observer standing near sonometer hears one *** per second. Calculate the speed with which the tuning fork is moved, if the velocity of sound in air is 300 m –1.

Answer 1

The fundamental frequency of the sonometer wire is

Actual frequency of the vibrating tuning fork = f = 400 Hz. The apparent frequency of the tuning fork is

where v = velocity of sound in air = 300 m *–1.

vs = velocity of the tuning fork, which is moving away from the vibrating wire.