Normal force question

[Chavi]

Can I please get some help with this tricky question:

A 1 kg ball is dropped vertically from a 2m height, and bounces back up again. 'Bounce time' is measured at 100ms.
1) Prove using calculations that the normal force is greater than Weight force.
2) Explain why

Thanks

[qshyrn]

1.just b4 the ball hits the ground its speed is 20ms-1 (due to 10ms-2 accel and freee fall of 2m) and its momentum is p=mv=20kgms-1
using impulse, Ft=delta P we get F=delta P/t =20/(100*10^-3)=20N which is higer than weight of 10N
2. obviously u nneed sigma F to be upwards cuz its acceleratig upwards so therefore the net force on object will be upwardss( from normal force)

[Chavi]

Thanks