A light pointer fixed to one prong of a tuning fork touches gnetly a smoked vertical plate. The fork is set vibrating and the plate is allowed to fall freely. 8 complete oscilllations are counted when the plate falls through 10cm.What is the frequency of the tuning fork?

Options

A. 280 Hz
B. 560 Hz
C. 56 Hz
D. 360 Hz

Answer

C

Explanation

This is the method of finding the frequency of a tuning fork by falling plate method. When the plate falls freely, the pointer attached to the vibrating fork produces a simple harmonic curve on the blackened surface of the plate.
The time of fall of the plate is calculated by using
`s = (1)/(2) "gt"^(2)`
`:. t = sqrt((2s)/(g)) = sqrt((2 xx 0.1)/(10)) = (1)/(sqrt50) s`
In this time, there are 8 oscillaions
`:.` Time for one oscillation `(T) = (1)/(8sqrt50)`
`:.` Frequency of oscillation
`= (1)/(T) = 8 sqrt50 div 8 xx 7 = 56 Hz`