If a raindrop falls under the influence of the downward gravitational force and the opposing resistive force. Consider a drop of mass 1.00 g falling from a height 1.00 km. It hits the ground with a speed of `50.0 ms^(-1)`. (1) What is the work done by the gravitational force ? (2) What is the work done by the unknown resistive force ?

Explanation

(1) The change in kinetic energy of the drop is
`DeltaK=(1)/(2)mv^(2)-0(1)/(2)xx10^(-3)xx50xx50=1.25j`
Work done by the gravitationl force is
`W_(g) = mgh = 10^(-3) xx 10 xx 10^(3)=10.0j`
(2) The work done by resistive force on the raindrop. Thus `W_(r) = DeltaK - W_(g)`
=1.25 - 10 = - 8.75 j