Consider a drop of rain water having mass 1g falling from a height of 1km. It hits the ground with a speed of 50m/s. Take g constant with a value of 10`m//s^(2)`. The work done by the(i) gravitational force and the (ii) resisitive force of air is

Explanation

Assuming that the drop was initially at rest, the change in the kinetic energy of the drop,
`Delta K = (1)/(2) mv ^(2)`
`= 1/2 xx xx (1 xx 10 ^(-3)) xx (50) ^(2)`
`= 1.25 kg m ^(2) s ^(-2) = 1.25 J`
The work done by the gravitational force,
`W _(s) = mgh`
`= 1 xx 10 ^(-3) ixx 10 xx 1 xx 10 ^(3)`
`= 10 J`