Question

A simple pendulum of length l has time-period T. It has a bob made of brass. Now we replace the brass bob by similar steel ball. (Density of steel = $\rho \times$ density of brass) and at the same time change the length so as to give a period of 2T. The new length is

• A. 2l
• B. 4l
• C. $4l\rho$
• D. $4l/\rho$

Answer 1

The correct option is B 4l

$T\alpha \sqrt{l}$ time period depends only on effective length$.$

Density has no effect on time period if length made $4$ times period becomes $2$ times$.$

Hence,

option $\left(B\right)$ is correct answer.