Understanding Angular Momentum: A Brief Explanation of Vector Cross Products

AI Thread Summary
The discussion centers on the calculation of angular momentum using vector cross products. Participants clarify that the cross product of unit vectors i and j results in k, while the reverse yields -k. The specific example of calculating 2.0(2.12i + 2.12j) x (-3.863i - 1.035j) is explored, leading to the conclusion that it simplifies to 2.0[-2.194k + 8.189k]. The conversation emphasizes understanding the foundational rules of vector multiplication to grasp the final results. Overall, the exchange highlights the importance of clarity in vector operations.
queenspublic
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When doing Angular Momentum, how is it that 2.0(2.12i + 2.12j) x (-3.863i - 1.035j) is equal to 2.0[-2.194k + 8.189k]?
 
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'cos i x j = k and j x i = -k (and ii = jj = 0) :wink:
 
tiny-tim said:
'cos i x j = k and j x i = -k (and ii = jj = 0) :wink:

I don't understand.

cos i x j = k ?

So cos 2.12i x 2.12j = -2.194k ?

Please explain it in numbers. How do I get -2.194k + 8.189k ?
 
queenspublic said:
I don't understand.

cos i x j = k ?

So cos 2.12i x 2.12j = -2.194k ?

he he :smile:

no, I meant because i x j = k :wink:
 
tiny-tim said:
he he :smile:

no, I meant because i x j = k :wink:

O! I get it! Thanks.
 

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