4 A particle is projected vertically upwards with speed \(u \mathrm {~m} \mathrm {~s} ^ { - 1 }\) from a point on horizontal ground. After 2 seconds, the height of the particle above the ground is 24 m .
- Show that \(u = 22\).
- The height of the particle above the ground is more than \(h \mathrm {~m}\) for a period of 3.6 s .
Find \(h\).