Two particle moving in the same direction with speeds `4 m//s` and `2m//s` collide elastically (the collision being head on). After collision , the velocity of first particle becomes `3 m//s` in the same direction . The velocity of the second should be

Options

A. `2 m//s` in same direction
B. `4 m//s` in same direction
C. `4 m//s` in opposite direction
D. `5 m//s` in same direction

Answer

D

Explanation

For elastic collision
`e = (v_(2) - v_(1))/(u_(1) - u_(2)) = 1`
`(v_(2) - 3)/(4 - 2) = 1`
`v_(2) = 5 m//s`