# moments

• May 4th 2009, 11:35 PM
manyarrows
moments
I am supposed to find the moment of the force at A about point O. Why do I keep getting zero, this can't be right. Where did I goof.

Attachment 11281

Thanks
• May 5th 2009, 11:46 AM
Jameson
I can't tell you where you went wrong, sorry. I wanted to say though that I looked over your work and all of your math looks good to me. Assuming you have the right $R_{ab}$, you did the right calculation for the unit vector. Your determinant calculation looks good to. So by my great powers of deduction it looks like your problem occurred determining the position or force vector. Hope this helps eliminate some doubt.
• May 5th 2009, 02:51 PM
manyarrows
Thanks for the effort. I will look over it again.
• May 5th 2009, 08:47 PM
CaptainBlack
Quote:

Originally Posted by manyarrows
I am supposed to find the moment of the force at A about point O. Why do I keep getting zero, this can't be right. Where did I goof.

Attachment 11281

Thanks

You have used the wrong R in the cross product.

CB