Is my teacher's work for collisions problem correct?

[toesockshoe]

Homework Statement

The problem and solution is here: http://nebula.deanza.edu/~Newton/4A/4AE2P3Winter10.jpg .

Homework Equations

The equations are in that link.

The Attempt at a Solution

My question is how do you know that the final velocities of both masses are equal to each other? wouldn't that ONLY be hte case if the collision was perfectly inelastic (which he didnt mention).

 

[haruspex]

how do you know that the final velocities of both masses are equal to each other? wouldn't that ONLY be hte case if the collision was perfectly inelastic (which he didnt mention).

I agree.

 

[toesockshoe]

I agree.

alright, and in this case it would be simply impossible for the masses to have the same velocity... because the first mass (the mass on the left) would move left after the collision correct?

 

[toesockshoe]

alright, and in this case it would be simply impossible for the masses to have the same velocity... because the first mass (the mass on the left) would move left after the collision correct?

nevermind scratch that... that would only happen if it is an elastic collision... this may or may not happen in an inelastic collision