Two bodies with masses of 200 and 500 g, moving towards each other, stopped after the collision

Two bodies with masses of 200 and 500 g, moving towards each other, stopped after the collision. What is the speed of the second body if the first was moving at a speed of 2 m / s.

m1 = 200 g = 0.2 kg.

m2 = 500 g = 0.5 kg.

V1 “= V2” = 0 m / s.

V1 = 2 m / s.

V2 -?

When interacting, the balls can be considered a closed system of interacting bodies, for which the law of conservation of momentum in vector form is valid: m1 * V1 + m2 * V2 = m1 * V1 “+ m2 * V2”.

Where m1 * V1, m2 * V2 are the impulses of the balls before the impact, m1 * V1 “, m2 * V2” are the impulses of the balls after the impact.

Since after the impact the balls stopped V1 “= V2” = 0 m / s, then the law of conservation of momentum takes the form: m1 * V1 + m2 * V2 = 0.

Since before the impact they were moving towards each other, then m1 * V1 – m2 * V2 = 0.

V2 = m1 * V1 / m2.

V2 = 0.2 kg * 2 m / s / 0.5 kg = 0.8 m / s.

Answer: the second ball was moving at a speed of V2 = 0.8 m / s before impact.