A plasticine ball flying horizontally at a speed of 8 m / s hits a wooden block and sticks to it.

A plasticine ball flying horizontally at a speed of 8 m / s hits a wooden block and sticks to it. The mass of the ball is 5 g, the mass of the bar is 15 g. Determine the speed of the bar after hitting the ball.

v1 = 8 m / s – the speed of the flying plasticine ball before colliding with the bar;

m1 = 5 grams = 0.005 kilograms – the mass of the plasticine ball;

m2 = 15 grams = 0.015 kilograms – the mass of a wooden block.

It is required to determine the speed of the bar after collision with the ball v2 (m / s).

Since after the collision the plasticine ball stuck to the wooden block, then according to the law of conservation of momentum:

m1 * v1 = (m1 + m2) * v2

v2 = m1 * v1 / (m1 + m2) = 0.005 * 8 / (0.005 + 0.015) = 0.04 / 0.02 = 2 m / s.

Answer: the speed of the wooden block after collision with the ball will be equal to 2 m / s.