Peter and Fred are skateboarding in a large semicircular halfpipe. Peter starts out from rest at a height h and collides with Fred standing at the bottom. Peter and Fred have about the same mass. After the collision, which height will Fred reach?

The answer is h/4

Explanation:

When Peter collides with Fred, the collision is inelastic & they both proceed with a velocity of V/2.

let m represent the masses for Peter & Fred

v represent the initial velocity of Peter

V represent final velocity of both of them

mv + 3m * 0 = (m+m) V

V = v/2

Using the expression; H = v² / 2g ... Eqn 1

Upon substitution of V/2 into Eqn 1 above,

H = (V/2) ² / 2g

H = (V²/4) : 2g

Therefore height will be h/4