Answer to Question #99762 in Mechanics | Relativity for Lara

Question

Theoretically, and according to Newton's second law, a car of mass m driven under a constant force of traction F should acquire a constant acceleration a=F/m. in practice, however, the car does not necessarily acquire the expected constant value of a. In fact, its acceleration is found to be a’< a, or it could move with a constant speed! Explain

Answer 1

In reality, an air resistance force acts on a car, which is proportional to the speed of the car squared. This force is directed against the movement of the car, thereby reducing the resulting force acting on the car, which leads to less acceleration of the car. And if this force is equal to the force that drives the car, then according to Newton’s first law, the car will move at a constant speed.