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?
It's being countered by friction between the car and the road.
To understand what is happening to the energy supplied by the engine, let's break down the concept of work, energy, and how they relate to the car's motion.
Work is done on an object when a force is applied to it, causing the object to move. In this case, the engine of the car applies a force to propel the car forward.
Energy, on the other hand, can exist in different forms. In this scenario, we are specifically talking about kinetic energy, which is the energy associated with a moving object.
The kinetic energy of an object can be calculated using the formula: KE = 1/2 * mass * velocity^2.
In the given situation, the car's speed is constant at 25 m/s. Since the kinetic energy depends on the square of the velocity, it means that the car's kinetic energy is also constant.
So, even though the car's engine is doing work on the car, maintaining its speed, the kinetic energy does not change because there is no change in velocity. The energy supplied by the engine is being exactly balanced by the energy lost due to external forces like friction (e.g., air resistance, rolling resistance) acting against the car.
Therefore, the energy supplied by the engine is being transferred to other forms of energy, mainly overcoming these external forces of resistance and keeping the car moving at a constant speed.