Two particles A and B, of masses 0.3 kg and 0.2 kg respectively, are attached to the ends of a light inextensible string which passes over a smooth fixed pulley. Particle B is held on the horizontal floor and particle A hangs in equilibrium. Particle B is released and each particle starts to move vertically with constant acceleration of magnitude a m s^-2.

1. Find the value of a.

Particle A hits the floor 1.2 s after it starts to move, and does not rebound upwards.

2. Show that A hits the floor with a speed of 2.4 m s^-1.
3. Find the gain in gravitational potential energy by B, from leaving the floor until reaching its greatest height.