Question

Two balls shown in figure are identical. Ball $A$ is moving towards right with a speed $v$ and the second ball is at rest. Assume all collisions to be elastic. Show that the speed of the balls remain unchanged after all the collisions have takes place (Assume frictionless surface)

Answer 1

Figure a ,b, c, d, e clearly shows how velocity if A is same

$v^{\prime }=\sqrt{v^2-2gh}$

At highest point above $h$ from initial position .

And then ball $B$ come to point $A$ with same velocity $v$ and after that elastic collision between $A$ and $B$ .

$B$ get rest and $A$ move with velocity $v$ by momentum conservation .