A ball with a mass of 1 kg moving from 1.8 km / h collides with a ball moving towards a meeting at a speed of 2 m / s.

A ball with a mass of 1 kg moving from 1.8 km / h collides with a ball moving towards a meeting at a speed of 2 m / s. Find the mass of the second ball if the bodies have stopped.

Let’s write the law of conservation of momentum:
p1-p2 = 0
m1v1-m2 * v2 = 0
Let us express the mass of the second ball from the equation:
m2 * v2 = m1 * v1
m2 = (m1 * v1) / v2
We plug in the known data and calculate the mass of the second ball:
m2 = (1 * 1.8) / 2 = 0.9 (kg)
Answer: 0.9 kg