2 A stone, of mass 6 kg , is thrown vertically upwards with a speed of \(12 \mathrm {~m} \mathrm {~s} ^ { - 1 }\) from a point at a height of 4 metres above ground level.
- Calculate the initial kinetic energy of the stone.
- Show that the kinetic energy of the stone when it hits the ground is 667 J , correct to three significant figures.
- Hence find the speed of the stone when it hits the ground.
- State two modelling assumptions that you have made.