By Newton's second law, the net force exerted on the object makes it undergo an acceleration a such that
(2 kg) a = 5 N
so that it is accelerated a = 2.5 m/s^2.
Since the object starts with velocity 3 m/s, after 7 s its acceleration will make it speed up to
3 m/s + (2.5 m/s^2) (7 s) = 20.5 m/s
