Plasticine balls are flying towards each other. Modules of their impulses are 3kg * m / s and 5kg * m / s, respectively.

Plasticine balls are flying towards each other. Modules of their impulses are 3kg * m / s and 5kg * m / s, respectively. Colliding, the balls stick together. Determine the momentum of the stuck together balls.

Р1 = 3 kg * m / s.

P2 = 5 kg * m / s.

R – ?

When the balls collide, an absolutely inelastic impact occurs, after which they begin to move together. Since the balls interact only with each other, then the law of conservation of momentum in vector form is valid for them. The vector sum of the pulses of the balls before and after the impact does not change: P1 + P2 = P.

Since the balls before the impact move towards each other, then for projections on the coordinate axis directed towards the motion of the first ball, the law of conservation of momentum will take the form: P1 – P2 = P.

P = 3 kg * m / s – 5 kg * m / s = – 2 kg * m / s.

The “-” sign indicates that after impact the balls will move in the opposite direction of the coordinate axis. That is, towards the movement of the second ball.

Answer: after the collision, the momentum of the balls will be P = 2 kg * m / s.