The period of a simple pendulum is double, when its length is increased by 1.2 m. The original length of the simple pendulum is

Options

A. 0.2 m
B. 0.3 m
C. 0.4 m
D. 0.5 m

Answer

C

Explanation

`(T_(2))/(T_(1))=sqrt((l_(1)+1.2)/(l_(1))) therefore (4)/(1)=(l_(1)+1.2)/(l_(1))`
`4l_(1)+l_(1)+1.2 therefore l_(1)=0.4m`