Question

A particle A is projected vertically upwards from a point O on horizontal ground with speed 20ms. At the same instant a particle B is released from rest at point P which is 30 m above the ground. The point P Is not directly above O ignore air resistance. Find thr time that elapses between B arrival on the ground and A arrival on the ground.
Ii) the speeds of A and B at the instant when they are at the same height and show that A and B are moving in opposite directions at this instant.