Question

A man of mass 80kg stands next to a stationary ball of mass 4kg on a frictionless surface. He kicks the ball forward along the surface with a speed 15m/s. Calculate the man’s recoil speed

Answer 1

Momentum is conserved.

p = m₁v₁ + m₂v₂ = constant

Momentum before the collision(kick):

p = 80 * 0 + 4 * 0 = 0

Momentum after the collision:
p = 80 * v₁ + 4 * 15 = 0

Solve for v₁.