Two billiard balls with the same mass m move towards one another. Ball one moves in the positive x-direction with a speed of v1i, and ball two moves in the negative x direction with a speed of v2i. The two balls collide elastically, and both balls change direction after collision. Write an expression for the horizontal component of the system’s initial momentum, Pix, in terms of m, v1i, and v2i.

(B) write an expression for the horizontal component of the system's final momentum, pfx, in terms of m and the final speeds of ball one, v1f, and ball two, v2f.

(C) if the initial speeds of the balls were v1i=2.0 m/s and v2i=1.0 m/s, what would be the final speed and direction of ball two, v2f, in meters per second?