Question

A light pointer fixed to one prong of a tuning fork touches a vertical smoked plate. The fork is set to vibration and the plate is allowed to fall freely. Eight complete waves are counted when the plate falls through 10 cm. The frequency of the tuning fork is

• A. 112 Hz
• B. 14Hz
• C. 28 Hz
• D. 56 Hz

Answer 1

The correct option is D

56 Hz

$t=\sqrt{\frac{2h}{g}}=\sqrt{\frac{2\times 0.1}{9.8}}=\frac{1}{7}s.$

$f=\frac{\text{number of waves}}{\text{time}}=\frac{8}{\frac{1}{7}}=56Hz$