Teach Fzx Tuesday - Geometric Momentum Problems

Two dimensional conservation of momentum problems are complicated.  For the conceptual physics student, even one dimensional momentum problems are often too complicated.  So I came up with an easier method.  Here's an example.

First we sketch before and after the collision.  That's the normal part.

Here's the normal solution which includes the (rather basic) algebra that turns off some students.

My Honors students can solve it that way pretty well but those negative signs give them difficulty.  Negative and positive only signify direction so let's use momentum vector arrows to solve the problems an easier way.

Compare.  Which would you prefer?  Both methods use identical concepts but the momentum arrows are cleaner and more intuitive.  Here are two solved problems.

It works in two dimensions too.

And with three objects.

My Honors Physics students solve problems better with this method.  Conceptual Physics students who are scared of math can now solve these problems more easily.  

I call this method "Geometric" Momentum Conservation and it works well even for some complicated two dimensional problems.  Let's make physics more accessible by SIMPLIFYING THE ALGEBRA whenever we can.