3 A particle \(P\) is projected vertically upwards, from a point \(O\), with a velocity of \(8 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). The point \(A\) is the highest point reached by \(P\). Find
- the speed of \(P\) when it is at the mid-point of \(O A\),
- the time taken for \(P\) to reach the mid-point of \(O A\) while moving upwards.