Body `A `of mass `m` and `B` of mass `3m` move towards each other with velocities `V and 2 V` respectivally from the positions as shown , along a smooth horizontal circule track of redius `r`. After the first elastic collision , they will collide again after the time:

Options

A. `(2 pi r)/(V)`
B. `(pi r)/(2V)`
C. `(pi r)/(V)`
D. `(2 pi r)/(3V)`

Answer

B

Explanation

`e = 1 = (Velocity of separation)/(2 V - (- V))`
Velocity of separation `= 3 V`
Required `= (2 pi r)/(3 V)`