A ball is projected vertically upwards from a platform 24 m above the ground. It reaches its greatest height 1.8 s after projection. The ball is modelled as a particle moving freely under gravity. Use g=9.8 m s−2g=9.8\text{ m s}^{-2}g=9.8 m s−2.
Find the speed of projection.
Find the speed with which the ball reaches the ground.
State one way in which the model could be refined.