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?

Explanation

Time taken by the plate to fall vertically through `h=10cm` is
`t=sqrt((2h)/(g))=sqrt((2xx10)/(980))=(1)/(7)s`
No. of vibrations recorded in `(1)/(7)s =8`
`:.` No. of vibrations of fork in 1 s `=(8)/(1//7)`
`=56Hz`