To find the work done when the kinetic energy of a body changes,
you can use the work-energy theorem,
which states that the work done on an object is equal to the change in its kinetic energy.
Given:
Initial kinetic energy, KE1=8 J
Final kinetic energy, KE2=12 J
The work done, W, is the change in kinetic energy:
W=KE2−KE1=12 J−8 J=4 J
Thus, the work done is 4 J, which is correct.