A car travels at a speed of 25 m/s on a flat stretch of road. The driver must maitain pressure on the accelerator to keep the car moving at a constant speed.
Are there any forces doing work on the car? Explain.
What is the net force?
The net force is zero.
The engine does work on the car, by applying a torque to the drive shaft. The work is necessary to overcome aerodynamic and internal (engine and bearing) friction.
The road applies a force to the tires to keep the car moving forward, but the road does not do work. The work is generated internally by the engine.
To determine whether there are any forces doing work on the car, we need to understand the concept of work and the forces acting on the car.
Work is defined as the product of the force applied on an object and the displacement of the object in the direction of the force. In other words, work is done when a force causes a displacement.
In the given scenario, the car is moving at a constant speed, which means it is not accelerating or decelerating. According to Newton's first law of motion (the law of inertia), an object at rest or moving at a constant speed will continue doing so unless acted upon by an external force.
The key concept here is that the car is not accelerating, which implies that the net force acting on the car is zero. If there were any forces doing work on the car, it would result in a change in its speed or direction, indicating acceleration and a non-zero net force.
Therefore, since the car is moving at a constant speed and not accelerating, we can conclude that no external forces are doing work on it.
However, there are internal forces doing work on the car. One such force is the force generated by the car's engine, which is transmitted through the accelerator and transmission system to propel the car forward. This force opposes the internal resistance forces, such as friction, air resistance, and rolling resistance.
The net force on the car is zero, as it is not accelerating. The engine force is balanced by the resistance forces, leading to a state of equilibrium.