# Does only the Tangential momentum count

1. Aug 24, 2004

### Gmaximus

Does only the Tangential momentum "count"....

When convertering the momentum from linear to angular?

2. Aug 24, 2004

### Staff: Mentor

For a particle with linear momentum $\vec p$, its angular momentum about some origin is $\vec L = \vec r \times \vec p$. So, if I understand what you're asking, the answer is yes.

3. Aug 24, 2004

### Gmaximus

So a particle traveling into a disc (thats free to rotate) in an inelastic collision that collides on a path tangent to the disc has all of its momentum converted into angular momentum, whearas a path of 30° with respect to the tanget line would have cos(30) times that angular momentum?

4. Aug 24, 2004

### Staff: Mentor

I'd phrase it a bit differently. (As I don't like saying that linear momentum "converts" to angular momentum.) Let me assume that the axis of the disk is fixed; the disk is free to rotate, but not translate. In any case, prior to the collision the particle has a certain angular momentum with respect to that axis. Yes, the amount of angular momentum it has depends on its direction of motion. During the collision, the angular momentum (of the entire system) does not change. Does this help?