Two plasticine balls move towards each other at speeds, moduli equal to 10 m / s and 20 m / s. The masses

Two plasticine balls move towards each other at speeds, moduli equal to 10 m / s and 20 m / s. The masses of the balls are 0.2 kg and 0.4 kg. Determine the modulus of the balls’ velocity after their absolutely inelastic collision.

Given:

m1 = 0.2 kilograms is the mass of the first ball;

v1 = 10 m / s – speed of the first ball;

m2 = 0.4 kilograms – the mass of the second ball;

v2 = 20 m / s – speed of the second ball.

It is required to determine the speed of the balls v (m / s) after an absolutely inelastic collision.

Since, according to the condition of the problem, the balls move towards each other, and the interaction is absolutely inelastic, then, according to the law of conservation of momentum (momentum):

m1 * v1 – m2 * v2 = v * (m1 + m2);

v = (m1 * v1 – m2 * v2) / (m1 +, 2) = (0.2 * 10 – 0.4 * 20) / (0.2 + 0.4) =

= (2 – 8) / 0.6 = -6 / 0.6 = -10 m / s.

The minus sign means that the speed of the bodies after the impact will be directed towards the motion of the second ball.

Answer: the module speed is 10 m / s.