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
`Delta K=(1)/(2)m upsilon^(2)-0=(1)/(2)xx10^(-3)xx50xx50=1.25 J`
Work done by the gravitational force is
`W_(g)=mgh=10^(-3)xx10xx10^(3)=10.0J`
(2) The work done by the resistive force on the raindrop.
Thus `W_(r )=Delta K - W_(g)=1.25-10=-8.75 J`