A simple pendulum completes 20 oscillations in 40 sec. Find its time period and frequency.

The time period is the time taken to complete one oscillation

$\text{ Hence time period }\mathrm{T}=\frac{40}{20}=2.0\sec$

$\text{ and frequency }\mathrm{v}=\mathrm{v}=\frac{1}{\mathrm{T}}=\frac{1}{2}=0.5 \mathrm{Hz}$