question_answer

A light points fixed to one prong of a tuning fork touches a vertical plate. The fork is set vibrating and the plate is allowed to fall freely. If eight oscillations are counted when the plate falls through 10 cm, the frequency of the tuning fork is:

A)  280 Hz                                 

B)  360 Hz

C)  56 Hz                                   

D)  56.0 Hz

Correct Answer: C

Solution :

Horizontal force cancil out at A and B and C \[{{F}_{u}}\]at \[A=2F\sin 60\] \[{{F}_{u}}\]at \[B=F\sin 60\] \[{{F}_{u}}\]at \[C=F\sin 60\] and point AB and C forces acts hence no equilibrium.