In the figure shown a lift goes downwards with a constant retardation. An observer in the lift observers a conical pendulam in the lift, revolving in a horizontal circle with time period 2 seconds. The distance between the centre of the circle and the point of suspension is 2.0 m. the retardation of the lift in `m//s^(2)` is

Options

A. `10 m//s^(2)`
B. `20 m//s^(2)`
C. `30 m//s^(2)`
D. `40 m//s^(2)`

Answer

A

Explanation

`T=2pisqrt((l cos theta)/(g_(eff)))=2pisqrt(h/(g_(eff)))`
`g_(eff)=g+a`, put T=2 ` rArr a=10 m//s^(2)` Retardation `10 m//s^(2)`