The 0.8-Mg car travels over the hill having the shape of a parabola. When the car is at point A, it is traveling at 9 m s and increasing its speed at . Determine both the resultant normal force and the resultant frictional force that all the wheels of the car exert on the road at this instant. Neglect the size of the car.

The drag force, fd, imposed by the surrounding air on a vehicle moving with velocity v is given by fd = cdaρv 2/2 where cd is a constant called the drag coefficient, a is the projected frontal area of the vehicle, and ρ is the air density. an automobile is moving at v = 80 kilometers per hour with cd = 0.28, a = 2.3 m2, and ρ = 1.2 kg/m3.