The velocity m, v m/s, of a particle is a straight line is given by

v = 6+pt+qt³

where t is the time in seconds after the particle passes through a fixed point O.

Given that t=2 s the distance of the particle from O is 16 m and its acceleration is 32m/s², calculate

a) the value of p and of q

b) the velocity of the particle at the instant when did acceleration is zero