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?
To determine if there are any forces doing work on the car, we need to understand the concepts of work and forces acting on an object.
1. Work: Work is defined as the transfer of energy that occurs when a force is applied to an object, and the object moves in the same direction as the force. In simpler terms, work is done when a force causes displacement.
2. Forces: There are different forces that can act on a car, including the force of friction, the force of gravity, and the force applied by the engine (thrust). In this scenario, we need to consider the forces acting on the car that contribute to keeping it moving at a constant speed.
In the case of the car moving at a constant speed on a flat road, there are two forces acting on it:
1. The force of friction: The car experiences frictional forces from the road, including rolling resistance and air resistance. These forces oppose the motion of the car and decrease its speed. However, since the car is traveling at a constant speed, these forces are balanced by the net force applied to the car.
2. The force applied by the engine: The car's engine applies a force in the forward direction to overcome the forces of friction. This force, known as the thrust or driving force, is responsible for keeping the car moving at a constant speed.
Now let's analyze if work is being done by these forces:
1. The force of friction: The force of friction does not do any work on the car because it acts in the opposite direction of the car's motion. In other words, the displacement and the force of friction are in opposite directions. Therefore, no work is done by the force of friction in this case.
2. The force applied by the engine: The force applied by the engine does work on the car. Since the car is moving at a constant speed, the force applied by the engine does positive work to overcome the resistance forces of friction. This work done by the engine's force is responsible for maintaining the car's constant speed.
Therefore, while the force of friction does not do any work, the force applied by the engine does work to maintain the car's constant speed.
Regarding the net force, we know that the car is moving at a constant speed, which means the net force acting on it is zero. The forward thrust from the engine equals and balances out the resistance forces, resulting in a net force of zero.