Question

At a given place, to increase the number of oscillations made by a simple pendulum in one minute from 72 to 90, the length of the pendulum is to be decreased by

• A. 64%
• B. 36%
• C. 50%
• D. 56%

Hint:

For a simple pendulum, the relationship between frequency ($f$) and length ($L$) is $f \propto 1/\sqrt{L}$. This implies $L \propto 1/f^2$. This proportionality is very useful for ratio-based problems, as you don't need to use the full formula with $g$ and $2\pi$.

Answer 1

The Correct Option is B