1. A 40 kg child, standing on a newly waxed floor, throws a 2 kg stone with a speed of 5 m/s. What is the child's recoil velocity?

2. A 1.6 x 10^-27 kg neutron traveling at 1 x 10^5 km/s collides with a stationary 3.34 x 10^-27 kg deuteron and combines to form a triton. What is the speed of this composite particle?

3. A 6 g bullet is fired into a 2 kg block at on the edge of a 1 m high table. If the bullet remains in the block and together they land 2 m horizontally from the edge of the table, what is the initial speed of the bullet?

4. A black 1 kg billiard ball moving at 3 m/s, (along the x-axis), strikes a pink 1 kg stationary ball. After the collision, the black ball moves at a 37 degree angle above the horizontal, and the pink ball moves off at a 53 degree angle below the horizontal. Find the magnitude of their velocities.