(i)[2]
Determine how long $P$ takes to return to the ground.
(ii)[4]
Let $t$ represent the number of seconds after $P$ is projected. At $t = 1$, a second particle $Q$ is launched vertically upwards at $10\,\text{m s}^{-1}$ from a point $5\,\text{m}$ above the ground. $P$ and $Q$ travel along different vertical lines. Determine the set of $t$ values for which the two particles are moving in the same direction.