A mass m moves with a velocity v and collides in elastically with another identical mass. After collision the 1st mass moves with velocity `v/(sqrt3)` in a direction perpendicular to the initial direction of motion. Find the speed of the 2nd mass after collision.

Options

A. `v`
B. `sqrt(3) v`
C. `2/(sqrt3) v`
D. `v/(sqrt(3))`

Answer

C

Explanation

In x-direction
`mv + 0 = 0 + mv_x implies mv = mv_x implies v_x = v`
In y-direction `0 + 0 = m(v/(sqrt3)) - mv_y , v_y = v/(sqrt3)`
`therefore` velocity of second mass after collision.
`v. = sqrt((v/(sqrt3))^2 + v^2) = sqrt(4/3 v^2) = 2/(sqrt3) v`