# Moment of Force

• Sep 11th 2006, 07:34 PM
ThePerfectHacker
Moment of Force
We are learning about moments. I have a question. The professor said that the Momemont vector can be expressed as,
$\displaystyle \bold{M}=\mbold{r}\times \bold{F}$
The question I have is are there any problems with this. Since the professor said the Moment changes signs depending on counterclockwise or not. Thus, I am asking if I use the cross-product I need not be concered about that, right?
• Sep 12th 2006, 01:18 AM
topsquark
Quote:

Originally Posted by ThePerfectHacker
We are learning about moments. I have a question. The professor said that the Momemont vector can be expressed as,
$\displaystyle \bold{M}=\mbold{r}\times \bold{F}$
The question I have is are there any problems with this. Since the professor said the Moment changes signs depending on counterclockwise or not. Thus, I am asking if I use the cross-product I need not be concered about that, right?

So long as you are using a "right-hand rule" to get the direction for the cross product (which I believe is standard in Math too?) you will be fine. Typically in Physics, as well as in Math, CCW is considered to be a positive rotation.

-Dan