1. A 1000kg boat is traveling across a lake when its engine is shut off. The magnitude of the frictional force between the water and the boat is proportional to the boat's speed (proportionality constant is 70) . Find the time it takes the boat to slow to one half its speed when the engine was shut off. 2. We have to solve this problem using newton's second law: F=ma 3. I thought about this problem for over a week now, and I really need all the help I can get!