Conservation of Momentum: Elastic Collision of Two Masses

[sciencec]

I really want to know which answer is correct. I don’t really know if I should include velocities to the left as negative velocities in the equation. Is it -1 or 4.33? Please help! Thanks!

 

[kuruman]

When you replace symbols with numbers, you must put negative signs where they belong. If v01 = +5 m/s and is moving to the right, then v03 = -3 m/s. The negative sign says that the second mass is moving in an opposite direction to that of the first mass. The same applies to the first mass after the collision. It is moving to the left so its velocity must be -1 m/s.