Question

what is velocity of ball at rest​

Answer 1

Answer:

Both balls have mass 'm'.

Initially ball 1 moves with v.

After collision ball 1 moves with v2

After collision ball 2 moves with 2v2

Momentum is conserved.

i.e.

mv=mv2+2mv2=3mv2

i.e. 

v2=3v

Velocity of approach =v−0=v

Velocity of separation =32v−31v=31v