Question

A simple pendulum attached to ceiling of lift has time period T when lift is at rest. Find its time period of lift if it starts accelerating upwards with acceleration g/2?

1. \(\sqrt {2\over 3} T\) 
2. \({\sqrt 2\over 3} T\) 
3. \({2\over \sqrt 3} T\)
4. \(T\over 3\)

Answer 1

The correct option is 1) \(\sqrt{2\over 3}T\) 

\(T=2\pi{ l\over g}\) 

\(T'=2\pi{ l\over g+{g\over2}}\) 

\(\therefore {T'\over T}={ \sqrt { g\over{ 3g \over2}}}\) 

\(T'=T{\sqrt 2\over3}\)