A 1500 kg car begins sliding down a 4.0 inclined road with a speed of 30km/hr. The engine is turned off and the only forces acting on the car are a frictional force from the road and a gravitational force. After the car havr traveled 40 metersl its speed is 40 km/hr.a. how much mechanical energy of the car reduced by frictional forceb. magnitude of frictionaj forcec. time elapsed in 50 m