A particle P starts from rest at a point O on a horizontal straight line. P moves along the line with constant acceleration and reaches a point A on the line with a speed of 30 m s^-1. At the instant that P leaves O, a particle Q is projected vertically upwards from the point A with a speed of 20 m s^-1. Subsequently P and Q collide at A. Find

1. the acceleration of P,
2. the distance OA.