Atugboat pulls a small barge through a harbor. the propeller thrust minus the drag produces a net thrust that varies linearly with speed. the combined weight of the tug and barge is 3600 kn. the relationship between force and velocity is plotted below: determine the time required to increase the speed from an initial value v1 = 1.0 m/s to a final value v2 = 2.5 m/s. the time required to increase the speed from an initial value v1 = 1.0 m/s to a final value v2 = 2.5 m/s is s