4 A small ball of mass 0.4 kg is released from rest at a point 5 m above horizontal ground. At the instant the ball hits the ground it loses 12.8 J of kinetic energy and starts to move upwards.
- Show that the greatest height above the ground that the ball reaches after hitting the ground is 1.8 m .
- Find the time taken for the ball's motion from its release until reaching this greatest height.