2 A particle \(P\) is projected vertically upwards from horizontal ground with speed \(15 \mathrm {~ms} ^ { - 1 }\).
- Find the speed of \(P\) when it is 10 m above the ground.
At the same instant that \(P\) is projected, a second particle \(Q\) is dropped from a height of 18 m above the ground in the same vertical line as \(P\). - Find the height above the ground at which the two particles collide.