Work out the mass of a ball and speed of a puck after collision and block's height when the speed is equal to v1/2.

1. Two balls are hung from cords. The first ball, of mass 1.5kg, is pulled to the side and released, reaching a speed of 2.1m/s at the bottom of its arc. Then, as shown in the figure, it hits and sticks to another ball. The speed of the pair just after the collision is 1.5 m/s .
What is the mass of the second ball?

2. A block slides down a smooth ramp, starting from rest at a height h. while it reaches the bottom it's moving at speed Vi. It then continues to slide up a second smooth ramp.
At what height is its speed equal to Vi /2?
(Answer is h/4, h/2, 3h/4, 3h/2, or 2h)

3. On a frictionless horizontal air table, puck A (with mass 0.255 kg ) is moving toward puck B (with mass 0.369 kg ), which is initially at rest. After the collision, puck A has velocity 0.118 m/s to the left and puck B has velocity 0.651 m/s to right.

a.) What was the speed of puck A before collision?
(Answer in m/s)

b.) compute? k, change in the total kinetic energy of the system that occurs during the collision.