Certain force acting on a 20 kg mass changes it velocity from `5ms^(-1) " to " 2 ms^(-1)`. Calculate the work done by the force ?

Explanation

Mass (m) = 20 kg
Initial velocity (u) = 5 m/s
Final velocity (v) = 2 m/s
Initial kinetic energy `=1/2"mu"^(2)=1/cancel(2)^(2) times cancel(20)^(10) times 5 times 5=250 J`
Final kinetic energy `=1/2mv^(2)=1/cancel(2) times cancel(20)^(10) times 2 times 2=40J`
Change in kinetic energy `=1/2 mv^(2)-1/2"mu"^(2)=40-250=-210J`
Change in kinetic energy stored as work done is -210 J.