Question

A 5kg. object travelling at 10m/s collides head-on with a 10kg. object travelling at 15m/s. If they were locked together after the collision, what is their velocity, and in what direction they will be heading?

Answer 1

$$MV-mv=(m+M)u\\(10)(15)-(5)(10)=(5+10)u\\u=6.67\frac{m}{s}$$

They will be heading in the direction of motion of a 10kg. object.