2. A 1000 kg boat is traveling at 60 km/h when its engine is shut off. The magnitude of the frictional force \(f_k\) between the boat and water is proportional to the speed \(v\) of the boat: \(f_k = 7v\), where \(v\) is in meters per second and \(f_k\) is in newtons. The time required for the boat to slow down to 30 km/h is (2) seconds.