A ball of mass `1kg` is suspended by an inextensible string `1m` long attached to a point O of a smooth horizontal bar resting on fixed smooth supports A and B. The ball is released from rest from the position when the string makes an angle `30^@` with the vertical. The mass of the bar is `4kg`. The displacement of bar when ball reaches the other extreme position (in m) is

Options

A. (a) `0.4`
B. (b) `0.2`
C. (c) `0.25`
D. (d) `0.5`

Answer

B

Explanation

Displacement of M relative to m on reaching the other end is `2L sin 30^@` or `1m`.

`4x=1(1-x)`
`:. x=0.2m`