Question

an object with a mass of 5kg is moving with an initial velocity of 20m/s.the object accelerates at a rate of 15m/s/s for 8s.what is the net force on the ball during acceleration?

Answer 1

It doesn't matter what the object's initial velocity is, or how long
the acceleration lasts.  All that matters is the object's mass and
acceleration.

Force = (mass) x (acceleration) =

                (5kg) x (15 m/s²) =

                         75 kg-m/s² = 75 newtons .