A car travels at a speed of 25 m/s on a flat stretch road. The driver must maintain pressure on the accelerator to keep the car moving at this speed.
The car's engine is doing work on the car, yet the kinetic energy of the car is not changing. What is happening to the energy supplied by the engine?
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To understand what is happening to the energy supplied by the engine in this scenario, we need to consider the concept of net work.
Work is defined as the transfer of energy from one object to another due to the application of force along the direction of displacement. In the case of a car traveling at a constant speed on a flat road, there is no change in kinetic energy. This implies that the net work being done on the car is zero.
When a car is moving at a constant speed, the forces acting on it are balanced. In this case, the force of friction (between the car's tires and the road surface) opposes the forward motion of the car and is equal in magnitude but opposite in direction to the driving force provided by the engine.
Since the net work is zero, the energy supplied by the engine is being used to do work against the frictional force. The engine is continuously providing energy to overcome the friction and maintain the car's speed. This energy is primarily lost as heat due to the friction between the tires and the road, as well as other factors like air resistance.
In summary, even though the engine is doing work on the car by supplying energy, the kinetic energy remains constant because the work being done by the engine is balanced by the work done against friction.