| A9-1 | Center of mass motion. |
| Purpose: | To show center of mass motion. |
| Description: | A freely swinging pendulum with massive bobs is mounted on an air track cart. As the pendulum swings back and forth, the air cart recoils in such a way that the center of mass remains at rest. |
| References: | Mp-1. |
| Equipment: | air track, glider with swinging pendulum. |