Question

A 5.0 kg object moving in the +x direction at 5.5 m/s collides head-on with a 3.1 kg object moving in the -x direction at 4.0 m/s. Find the final velocity of each mass for each of the following situations. (Take the positive direction to be +x.)
The bodies stick together.
m/s (5.0 kg mass)
m/s (3.1 kg mass)

Answer 1

The bodies stick together: non elastic, use conservation of momentum.
M1*V1+M2*V2=(M1+M2)Vf