Having problem in crossproduct, dotproduct.

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The discussion revolves around the application of angular momentum in a rigid body collision simulation, specifically the equation L = p x r, where p represents momentum and r is the distance vector to the collision point. The user initially confused the use of cross product and dot product in their calculations, questioning the necessity of a third dimension in a 2D system. They clarified that the angular momentum should indeed be calculated using the cross product, not the dot product, as the resultant vector resides in a third dimension. Ultimately, the user resolved their confusion and confirmed that the correct approach involves using the cross product. This highlights the importance of understanding vector operations in physics simulations.
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[SOLVED] Having problem in crossproduct, dotproduct.

Sorry, i have a lil problem in solving for some math in physics equation.
I'm doing simulation of rigid body collision reaction,
and i applied the angular momentum,
which is L = p x r = I ( w2 - w1);
where p = mv is the impact of the collision,
w1,w2 is the angular velocity.
r be the vector from the center of body to the collision point.

I'm wondering if the eq is p x r,
in a 2D system, the third coordinate system is ignored.
and in some circumstances,
i let the equation to be reformed into something like p * n x r,
where n is the reflect/normal vector at the collision point.
since p x r is actually the cross-product,
but some books are telling me to take dotproduct of it,

i'm wondering and hoping to seek for help.

Thanks in advance.
 
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L=p x r= pr sin (a), where a is the smaller angle between p and r. The resultant vector L requires and resides in a third dimension by definition. The angular velocity omega (w), parallel to L, also lies in this third dimension.

Given p (momentum) and r (momentum arm), you do not find the angular momentum by taking their "dot product."

What two-dimensional system did you have in mind?
 
bleessh i just found that i got it figured, just it skipped few steps n i did proved it, not actually dotproduct of them, but cross of them ^^
 
So I know that electrons are fundamental, there's no 'material' that makes them up, it's like talking about a colour itself rather than a car or a flower. Now protons and neutrons and quarks and whatever other stuff is there fundamentally, I want someone to kind of teach me these, I have a lot of questions that books might not give the answer in the way I understand. Thanks
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