physics question dealing with collisions. please help!!?

Question

An object has a mass of 40 kg and a velocity of 10m/s. It collides with two masses (each mass 40 kg) attached to each other and moving with a velocity of 2 m/s. All three objects are stuck together after collision. What is the velocity of the three masses after collision?

Answer 1

It depends on the relative direction of the single 40 kg object's velocity versus the 2 40 kg objects' velocity.

The equation for completely inelastic collisions (where they stick together) is
m1*u1 + (m2+m3)*u2 = (m1+m2+m3)*v