1. They take the risk because this push can give each new
     skater a boost of speed.

2. Impulse given to skater 51 is 225 kg*m/s to the RIGHT

3. Impulse given to skater 52 is 225 kg*m/s to the LEFT

4. Velocity of skater 51 after the collision is 5.4 m/s to the left
            (lower than original 9 m/s)

5. Velocity of skater 52 after the collision is 9.3 m/s to the left
            (faster than original 6 m/s)

6. Kinetic energy before = 3735 J, after = 3840 J, no, not conserved

7. Momentum before 966 kg*m/s to left, after 966 kg*m/s, yes, is conserved

8. Put the most massive stater in third spot, least massive skater
            fourth spot.  The boost due to push will be largest
            when the pusher is massive and the pushee is lightweight.