the force that acted upon the body in for it to begin moving is represented by the equation:
F = ma
where F isis force, m is mass, and a is acceleration.
we know the mass is 4 kg.
we know the speed and the amount of time it took to get that speed. the amount of time it takes to reach a speed is acceleration. the equation for this is
a = (delta v) / t
a is acceleration. delta v is change in velocity. t is time.
So
a =(8 - 0 ) / 2
a = 4
F =4 * 4
F = 16 N