Direction of torque

1. Nov 16, 2005

Kenny Lee

As I understand, precession (of top) occurs because the torque generated by weight causes a change in the angular momentum of spin. Since the angular momentum of spin is along the axis of rotation, precession results.

Here I can 'picture' the directional nature of torque.

But lets say if there was no spin, and there was a torque generated about the contact point because of weight anyway. The top topples over as a result; why doesn't the motion of the top coincide with the direction of torque.

Now that I think about what I've said, it doesn't really make sense...
Any advice would be appreciated. Thanks.

2. Nov 16, 2005

BerryBoy

What do you mean? It does...
Either that or I don't understand your wording.

Can you draw a picture? It might help me understand what you're trying to say.

Regards,
Sam

3. Nov 16, 2005

Kenny Lee

Was about to draw it; but decided that I could just explain in terms of a balance beam. ITs just that when I put it this way, I sound so stupid...
Okay... so I exert a force on the end of a balance beam, and a torque is generated about the pivot. The direction of torque goes into the page (if we draw it, viewed from the side). Why doesn't the motion go 'into' the page... see, sounds stupid. I just want some way, IF there is anyway at all, to 'picture' torque...
Anyway, same thing with the top. When its not spinning it topples over just like the balance beam would. How does the direction of torque 'show' itself.
With precession, I can sorta understand. Its just that what I understand seems to contradict with what happens when there is no spin.

Last edited: Nov 16, 2005
4. Nov 16, 2005

BerryBoy

The way I picture net torque on an object, is that it is the axis on which the object will rotate about.