Question

A simple pendulum of length l has a brass bob attached at its lower end. Its period is T. If a steel bob of same size, having density x times that of brass, replaces the brass bob and its length is changed so that period becomes 2T, then new length is

• A. 2 l
• B. 4 l
• C. 4 l x
• D. $\frac { 4 l } { x }$

Answer 1

Answer: (B)

4 l

Answer 2

$T \propto \sqrt { l }$ Time period depends only on effective length. Density has no effect on time period. If length made 4 times then time period becomes 2 times.