A ball of mass m falls vertically to the ground from a height h1 and rebound to a height h2. The change in momentum of the ball on striking the ground is

When ball falls vertically downward from height h1 its velocity v2→ = 2gh2Change in momentum∆P→ = m(v2→-v1→) = m(2gh1+2gh2)(because v1→ and v2→ are opposite in direction)