# HELP! HW10 Problem 6

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In this question, v1i=v2i (because v=sqrt(2gh), it doesnt matter the mass). So from elastic collision equations , I get v1f=v1i (because v1i=v2i, so the numerator and denominator are the same, m1+m2). Similarly, we get v2f=v2i, so the heights (for both blocks) after collision are exactly the same as the heights the blocks released. Webassign says that's wrong. Please HELP, THANKS.

Use the elastic collision equations there, you will find the final velocities -- pay attention to the directions (signs) of the velocities -- $v_{2i}$ is in the negative x direction so you will need to put in a negative sign there.