1. A 50 kg girl throws a 7 kg medicine ball at 10 m/s to a 40 kg boy. If both are on a frictionless lake, what are both children's recoil velocities?

2. A 200 kg lifeboat carries two people, 50 kg and 80 kg respectively. If each dive off opposite ends of the boat at 4 m/s, what is the velocity of the boat immediately after?

3. If all 240 million people in the U.S., each having an average mass of 60 kg, all jump up simultaneously at 6 m/s, what would be the approximate recoil velocity of the earth?

4. A cannon is mounted on the back of an ice sled. Together, the cannon and sled have a mass of 4,000 kg. If a 50 kg shell is now loaded into the cannon and fired horizontally at 150 m/s, what is the speed of the sled after firing the cannon?

5. A shell moving at 10 km/s separates into two identical pieces that continue to move in the same direction, if one piece moves at 4 km/s, what is the speed of the other fragment?

6. The same shell in the previous problem again breaks up in to two fragments of equal mass. One fragment travels at 4 km/s in the opposite direction to the initial direction of the shell. What is the velocity of the other fragment?