Question

Concerning Newton's Cradle:
a) Determine the velocity of ball 2 just after the collision in terms of vi.

Also I am having problems with the following question: A boy moves on a skateboard at a constant velocity of 3 m/s. The combined mass of the boy and the skateboard is 40 kg. He catches a bag of flour of mass 5 kg that is thrown to him horizontally at 6 m/s. Determine the velocity of the boy after catching the bag of flour.

Any help would be greatly appreciated! Thanks sooooo much for this website....