1. Momentum Vector Analysis Pages 251 – 255 – 256 – 264
Created for CVCA Physics By
Dick Heckathorn
5 Jan 2K + 5

2. Page 251 Masses Equal One Moving, one at rest
Page 255 Masses Equal Both Moving
Page 256 Masses Unequal Both Moving
Page 264 Masses Unequal Both Moving From Center of Mass Point of View

3. Page 251 Equal masses

4. Page 255 Equal masses

5. Page 256 Unequal masses

6. Center of Mass
1. Some point (in any object) where the entire mass of the object can be considered to act.

7. Center of Mass
2. Has a great deal of significance when dealing with the conservation of momentum.

8. Center of Mass of 2 Ball System
If mass is equal, it is equal distance from the two balls on a line connecting the two balls.
If mass is not equal, then it is closer to the larger mass.

9. Center of Mass of 2 Ball System
In the following drawing, the masses are in a ration of 7:3, so the ratio of the distance from each ball to the center of mass is in the inverse ratio of 3:7.

10. Center of Mass of 2 Ball System
You will see that the center of mass is moving with a constant velocity as they are equally spaced.
If the center of mass is where all the mass can be considered to be located, it should be moving at constant velocity both before and after the collision.

11. Page 264 Center of Mass

12. Center of Mass of 2 Ball System
The center of mass is indeed a special point. Since the collision is an isolated system, and according to Newton’s law, it must move at constant velocity if no outside force is acting on the system.

13. Center of Mass of 2 Ball System
If we move along with the center of mass, using it as our frame of reference, the total momentum is zero.

14. That’s all folks!