As a car goes faster, the air resistance or drag force on the car increases. This is because the faster a car moves, the more air molecules collide with its surface, and this collision generates more drag force. As a result, it requires more energy to maintain the speed of the car at a higher rate, and the engine has to work harder to overcome the increased air resistance. This phenomenon limits the top speed of a car and is one of the reasons why fuel efficiency decreases as speed increases.
