Certain force acting on a 20 kg mass changes its velocity from 5 m s–1 to 2 m s–1 . Calculate the work done by the force.

Mass of the body (m) = 20 kg

Initial velocity (u) = 5 m/s

Final velocity (v) = 2 m/s

We know that,

Work done (W) = Change in kinetic Energy

=${1\over2}$mu² −${1\over2}$mv²

=${1\over2}$m(u² − v² )

=${1\over2}$(20)(5² − 2² )

= 10(25 − 4)

= 210 J