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 2 T, then new length is

Options

A. `4//x`
B. `(4l)/(x)`
C. 4l
D. 2l

Answer

C

Explanation

`T=2pi sqrt((l)/(g))`
T depends upon l but the material (density ) of the bob has no effect on T.
To change the period from T to 2T, the length should be increased to four times or 4l.