Question

If a pendulum takes $4sec$ to swing in each direction, find the length of the pendulum.

• A. 4.2 m
• B. 3.97 m
• C. 5.2 m
• D. 15.9 m

Answer 1

The correct option is D 15.9 m

Given: The pendulum takes 4sec to swing in each direction, which means it swings in one side of the pendulum for 4 sec.
So, half time period, $\frac{T}{2}=4sec$

Time period of simple pendulum, $T=2\times 4=8s$

$T=2\pi \sqrt{\frac{l}{g}}$
$\Rightarrow 8=2\pi \sqrt{\frac{l}{10}}$
$\Rightarrow l=\frac{64\times 10}{4\times {\pi }^2}$

$\Rightarrow l\approx 15.9m$