Collision Problem: Find Mass of Second Box

[cjmagic]

A 5 kg box with initial velocity of 2 m/s collides with another box at rest. They stick together after the collision with a final velocity of .5 m/s.

A. Find the mass of the second box.
Here is tried using the conservation of momentum by setting the initial to the final but it isn't seeming to work.

B. If the 5 kg box bounced back with a velocity of 2 m/s what will be the velocity of the second box.
Can't do this because I am unable to find the mass of the second box from problem A.

 

[Doc Al]

A. Find the mass of the second box.
Here is tried using the conservation of momentum by setting the initial to the final but it isn't seeming to work.

Show what you did. What equation did you use for conservation of momentum?