posted by Natasha .
A 1100-kg car is being driven up a 4.0° hill. The frictional force is directed opposite to the motion of the car and has a magnitude of f = 518 N. A force is applied to the car by the road and propels the car forward. In addition to these two forces, two other forces act on the car: its weight and the normal force N directed perpendicular to the road surface. The length of the road up the hill is 310 m. What should be the magnitude of , so that the net work done by all the forces acting on the car is +140 kJ?