2 A particle \(P\) of mass 0.4 kg is projected vertically upwards from horizontal ground with speed \(10 \mathrm {~m} \mathrm {~s} ^ { - 1 }\).
- Find the greatest height above the ground reached by \(P\).
When \(P\) reaches the ground again, it bounces vertically upwards. At the first instant that it hits the ground, \(P\) loses 7.2 J of energy. - Find the time between the first and second instants at which \(P\) hits the ground.