# collision with frictions dealt using tangent impulses

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I was reading Bourg's "physics for game developers" second edition.
In page 117(chapter 5,Friction) , what confused me is the way to apply the tangent impulse.
The book writes :

[attachment=23871:formular.jpg]

v1+  is the velocity of body1 after the collision between body1 and body2.
v2+ is the velocity of body2 after the collision between body1 and body2.
why v1+ and v2+ both + (uJ)t/m1 ?
In my opinion,the right way to apply the tangent impulse is like this:
v1+ = ... + (uJ)t/m1
v2+ = ... - (uJ)t/m2

What's wrong?
Edited by gofordream

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Probably a typo. The tangent impulses must be equal and opposite as well.

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Probably a typo. The tangent impulses must be equal and opposite as well.

I was agree with your second sentence.
But I also see this book's first edition and it's source code. It is consistent with those four formulas, so I don't think it's a typo.Maybe there is something I don't understand?

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I'd advise using almost any resource apart from that Bourg book.

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