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

Options

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

Answer

C

Explanation

Time required by vertical plates to fall through 10 cm is given by `h=ut+(1)/(2)g t^(2)`
or, `10=(1)/(2)xx980xxt^(2)` [taking `g=980cm//sec^(2)`]
or, `t^(2)=(1)/(49)impliest=(1)/(7)` seconds.
The tuning fork completes 8 oscillations in `1/7` seconds.
`therefore` Time period, `T=(1)/(7)-:8=(1)/(56)s`.
`therefore` Frequency of the fork, `f=1//T=56Hz`.