Question

Two billiard balls with the same mass m move in the direction of one another. Ball one travels in the positive x-direction with a speed of V1i, and ball two travels in the negative x-direction with a speed of V2i. The two balls collide elastically, and both balls change direction after collision. If the initial speeds of the balls were v1i=2.0m/s and v2i =1.0m/s, what would be the final speed and direction of ball two, v2f, in m/s?

Answer 1

V2f = 2 m/s

Step-by-step explanation:

From conservation of energy, since the momentum is conserved, we can use the formula ;

MV1i + MV2i = MV1f + MV2f

Divide each term by M to get;

V1i + V2i = V1f + V2f

From the question, V1i = 2 m/s and V2i = 1 m/s.

Thus;

2 + 1 = V1f + V2f

However, because momentum is conserved, V1i will be equal to V2f.

Thus, V2f = 2 m/s