Answer:
magnitude of v = 2.5 m/s, and in the same direction as the initial velocity of the 5 kg ball.
Explanation:
We use conservation of linear momentum in an elastic collision to solve for the unknown velocity v:
Pi = Pf
5 kg * 5 m/s + 10 kg * 0 m/s = 5 kg * 0 m/s + 10 kg * v
25 kg m/s = 10 kg * v
v = 25/10 m/s
v = 2.5 m/s
and in the same direction as the initial velocity of the 5 kg ball.