Question

what is the work that needs to be done to increase the speed of a 1kg ball from 2m/s to 4m/s

Answer 1

work done should be difference of kinetic energies, so 0.5*1*(4^2-2^2)=6

Answer 2

Workdone = Change in Kinetic Energy

W = 1/2mv2-1/2mu2

W = {[1/2×1×(4×4)]-[1/2×1×(2×2)]} Joule

W = (8-2) Joule

Workdone = 6 Joule