| Sample Problems for Monday, July 20, 2009 Collisions, Center of Mass, Rockets |
| Separation Angle of Colliding Billiard Balls |
| Leaping from a Small Boat |
| Collisional Ionization of Hydrogen |
| Velocity Amplifier |
| The Sun-Jupiter Mass Center |
| The Mass Center of a System of Particles |
| The Mass Center of a Cone |
| A Nearly Relativistic Rocket |