Q120 / 125 · BITSAT 2017 · Physics

Two simple pendulums of lengths $5 m$ and $20 m$ respectively are given small displacement in one direction at the same time they will again be in the same sense when the pendulum of shorter length has completed $n$ oscillations. Then, $n$ is

Solution

According to question

$n_{1} T_{1} = n_{2} T_{2}$

$\Rightarrow n \cdot 2 π \sqrt{\frac{5}{g}} = (n - 1) 2 π \sqrt{\frac{20}{g}}$

$\frac{n}{n - 1} = 2 \Rightarrow n = 2$

Hence, the correct answer is option: 'C'.