Torque and Angular Momentum Vector Question.

[sdefresco]

Hello. I'm currently entering into a Physics II class at the start of my third semester at UCONN (my first semester was introductory modern physics - kinetic theory, hard-sphere atoms, electricity and magnetism, scattering, special relativity, Bohr model, etc), and finished Physics I off with torque and angular momentum before icing it with pendula, harmonic motion, and the wave equation. Of all of this, figuring torque out was the hardest of all.

I understand why its vector points in or out of the page (z axis) mathematically as a cross-product, but is this arrow simply symbolic of the spin-direction, or is it something more than simply a way of telling spin. As in, can there be any reflection of this defined vector more directly.

I also understand torque is too a tensor, so I accept that may be relevant to my question.

 

[Delta2]

In simple words, the direction of the torque and of the angular momentum give us the direction of the axis of rotation. So in your example with the page, the torque is such that the axis of rotation (the rotation that will happen if that torque is the total torque acting on the body) will be vertical to the plane of the page. Whether it is in or out of the page give us info on whether it is clockwise or counter-clockwise rotation.