What is inertia with example 1

Law of inertia

In this article on physics, we deal with the law of inertia - often also referred to as Newton's 1st law. We provide important knowledge that can be used in physics lessons as well as in everyday life.

Before we get into the subject of the law of inertia, you should read the following headings. If these topics seem unfamiliar to you, you should read them up. Without this knowledge, you may have problems understanding this article.


Law of Inertia: 1. Newton's Law

From everyday experiences everyone knows that you have to use a force to change the state of motion of a body. For example, if you want to transport an object to another room, you have to use strength to do so. For example, an acceleration must be carried out in the initial phase in order to pick up the object. And a force must also act when there is a change in direction. The English physicist Isaac Newton, who lived from 1643 to 1727, already established this. His knowledge went down in history as that Newton's Laws and apply to the total force. The first of these was called the Law of Inertia. This says:

Every body maintains its speed in terms of magnitude and direction as long as it is not forced by external forces to change its state of motion.


  • A body is at rest, i.e. its speed is zero. If there is no force acting on this body, it remains motionless.
  • A body moves at 20m / s in a certain direction. As long as there is no force acting on it, it maintains the speed of 20m / s and its direction.

Important note:

The law of inertia - and also the other Newtonian laws - is a so-called axiom. The axioms of physics are not the results of pure thinking, but are based on experience and have proven themselves in their application to the real world.


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