Conservation of momentum only applies when there are no external forces, so how would I add friction into the equation?(adsbygoogle = window.adsbygoogle || []).push({});

For a sticky collision,

[tex]p_{A1}+p_{B1}=p_{A2}+p_{B2}[/tex]

But I've seen that the momentum after is usually less than the momentum before (for a sticky, linear collision of 2 carts on a track)

Would I add the force of friction of each cart to the left side of the equation? So

[tex]p_{A1}+p_{B1}+f_{A1}dt+f_{B1}dt=p_{A2}+p_{B2}[/tex]

But the collision itself seems like .0001 seconds so it doesn't really help... How could I form an equation to explain the loss of momentum?

And finally, if two carts of the same weight are traveling at each other, their forces of friction would cancel out so the conservation of momentum would apply?

Thank you!

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# Momentum & Friction

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