Serway & Jewett — Rotation of a Rigid Object about a Fixed Axis: Problem 30

Why is the following situation impossible? In a large city with an air-pollution problem, a bus has no combustion engine. It runs over its citywide route on energy drawn from a large, rapidly rotating flywheel under the floor of the bus. The flywheel is spun up to its maximum rotation rate of \(3\,000\text{ rev/min}\) by an electric motor at the bus terminal. Every time the bus speeds up, the flywheel slows down slightly. The bus is equipped with regenerative braking so that the flywheel can speed up when the bus slows down. The flywheel is a uniform solid cylinder with mass \(1\,200\text{ kg}\) and radius \(0.500\text{ m}\). The bus body does work against air resistance and rolling resistance at the average rate of \(25.0\text{ hp}\) as it travels its route with an average speed of \(35.0\text{ km/h}\).