# Homework Help: Angular momentum of rigid body elements tensor

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1. Apr 12, 2015

### ognik

1. The problem statement, all variables and given/known data
I was working through my text on deriving the tensor for Angular momentum of the sums of elements of a rigid body, I follow it all except for one step. Here is a great page which shows the derivation nicely - http://www.kwon3d.com/theory/moi/iten.html
I follow clearly to the Eq. below
2. Relevant equations
$$H= \sum_{i} m_{i} [ r_{i}\wedge(\omega\wedge r_{i})]$$

3. The attempt at a solution
The link is as far as I could get, could someone please explain how it goes from the above Eq. to the 3 matrices in the next step?

2. Apr 12, 2015

### Delta²

Last edited: Apr 12, 2015
3. Apr 12, 2015

### ognik

Thanks, indeed it does - "The vector cross product also can be expressed as the product of a skew-symmetric matrix and a vector" (not in my text book, naughty, bad text book :-))
I also did the (laborious) 'normal' triple vector product calculations, and happily ended with the same answer - guess which way I will be evaluating triple vector products from now on :-)