Question

A person driving a car suddenly applies the brakes on seeing a child on the road ahead. If he is not wearing the seat belt, he falls forward and hits his head against the steering wheel. Why?

Answer 1

The first law says that unless acted on by a net external force, an object at rest will remain at rest and an object in motion will remain in motion. In mathematics, this is similar to asserting that if an object's net force is zero, the object's velocity is constant.

Complete answer:
The resistance of any physical object to any change in velocity is known as inertia. Changes in the object's speed or direction of motion are included. The tendency of things to continue travelling in a straight path at a steady speed when no forces operate on them is one example of this characteristic.

The word inertia is derived from the Latin word iners, which means idle or slow. Mass, which is a quantitative characteristic of physical systems, manifests itself in inertia as one of its fundamental forms. The notion of inertia is a fundamental concept in classical physics that is still used to describe how things move and are influenced by applied forces.

The notion of inertia was established by Galileo, a leading scientist in the seventeenth century. Moving things eventually come to a halt due to a force known as friction, according to Galileo. Galileo discovered that a ball will roll down one plane and up the opposing plane to roughly the same height in tests employing a pair of inclined planes facing each other. The ball would roll up the opposing plane even closer to the original height if smoother planes were employed.

Any difference between the original and ultimate heights, Galileo reasoned, was attributable to friction. Galileo proposed that if friction could be completely eliminated, the ball would rise to the same precise height.When a person abruptly hits the brakes, the bottom portion of the person slows down with the car, but the top part of the driver continues to travel at the same speed in the same direction owing to inertia, and his head car collides with the steering.

Note: The knowledge of inertial reference frames acquired by Galileo and Newton formed the foundation for Albert Einstein's special relativity theory, which he postulated in his 1905 article "On the Electrodynamics of Moving Bodies." While Einstein's groundbreaking theory transformed the meaning of several Newtonian notions including mass, energy, and distance, the idea of inertia remained intact from Newton's original meaning. However, this resulted in a particular relativity limitation: the theory of relativity could only be applied to inertial reference frames.