(i)[3]
Find the length of time during which $P$'s height above the ground is greater than $15\,\text{m}$.
(ii)[5]
Find the velocities of $P$ and $Q$ at the instant when both particles are at the same height.
Mathematics 9709 · AS & A Level · Kinematics of motion in a straight line
Kinematics of motion in a straight line — practice question
Particles $P$ and $Q$ are projected vertically upwards from two separate points on level ground, with speeds of $20\,\text{m}\,\text{s}^{-1}$ and $25\,\text{m}\,\text{s}^{-1}$ respectively. $Q$ is launched $0.4\,\text{s}$ after $P$.