1 A particle \(B\) of mass 5 kg is at rest on a smooth horizontal table. A particle \(A\) of mass 2.5 kg moves on the table with a speed of \(6 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) and collides directly with \(B\). In the collision the two particles coalesce.

1. Find the speed of the combined particle after the collision.
2. Find the loss of kinetic energy of the system due to the collision.