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Oct 20, 2008

Homework Problem 3/269


Suggestions:
Draw FBD's of A alone, B alone and A+B together. From these FBD's:
  1. From A alone, you know that momentum of A is conserved in the y-direction.
  2. From B alone, you know that momentum of B is conserved in the y-direction.
  3. From A+B together, you know that momentum of A+B is conserved in the x-direction.
These give you three equations. The fourth equation is the coefficient of restitution equation relating the differences in the x-components of velocity for A and B.

Let us know if you have any questions on this.

2 comments:

garrettmocas said...

I used the e equation and the other, longer equation and solved them both for Va2x and then set them equal and could not get the correct solution. Any ideas?

Lindsey VanDeMark said...

that sounds like it should work. The e equation should be .75=(Vb'-Va')/(Va-Vb) all in the x direction so you have to remember Vbx is a negative. The other equation should be Va+Vb=Va'+Vb' because the masses are all the same and therefore cancel out. solve these simultaneously and they should come out correct. Don't forget to find the magnitude using your x and y component. These equations only give you the x component.

This is what I did, hope it helps.