Final answer:
The force that accelerates a car on a level road is exerted by the tires on the road, where the road pushes forward on the tires. The net force leads to acceleration and on a curve, friction provides the centripetal force necessary for turning.
Step-by-step explanation:
The force that accelerates a car on a level road is exerted by the tires on the road. When the engine generates power, it is transferred through the gears to the axle, and finally to the wheels. The tires then push against the road with a force directed backward. According to Newton’s third law, for every action, there is an equal and opposite reaction. So, the road pushes forward on the tires with an equal force. This forward force from the road on the tires is what accelerates the car.
When analyzing forces acting on a car, it's important to consider the net force and the acceleration of the car. If the car is on a slick road with no friction, these forces change. For a car moving at constant velocity, the net force is zero because all forces balance out. However, if the car is accelerating, this indicates that there is a net force acting on it. This net force is due to the excess force generated by the car's tires pushing on the road, overcoming any friction or drag forces.
On a curve, the friction force between the tires and the road provides the necessary centripetal force to keep the car moving in a circular path. If this frictional force is insufficient, the car would not follow the desired path, illustrating the crucial role of friction in vehicle dynamics.