make all this shorter and simplify it

Definition of the Law: Newton's First Law of Motion, often referred to as the Law of Inertia, states that an object at rest will remain at rest, and an object in motion will continue moving in a straight line at a constant speed, unless acted upon by a net external force. This law emphasizes the concept that objects tend to maintain their state of motion unless influenced by an external force.

Real-World Example
Example: A Book on a Table Imagine a book sitting on a table. The book remains at rest until someone applies a force to lift or push it. Conversely, if you slide the book across the table, it will eventually come to a stop due to friction, which is an external force acting on it.

Explanation of How the Example Demonstrates the Law
In the example of the book on a table, the law of inertia is illustrated through the book's behavior in the absence and presence of forces. Initially, the book remains at rest, demonstrating that it will not move unless a force is applied (the force exerted when you pick it up or push it). This aligns with the law’s assertion that an object will maintain its state unless a net external force acts upon it.

When you slide the book across the table, it moves due to the force you applied. However, it eventually comes to a stop because of friction, which is an external force opposing its motion. This highlights another aspect of inertia: not only do objects resist changes in their state of rest, but they also resist changes in their motion unless acted upon by an external force. Thus, the book perfectly encapsulates the principles laid out in Newton's First Law.

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Newton's First Law of Motion (Law of Inertia): An object at rest stays at rest, and an object in motion continues at a constant speed in a straight line unless acted on by an external force.

Example: A book on a table remains still until someone lifts or pushes it. If you slide it, it eventually stops due to friction, an external force.

Explanation: The book's behavior shows inertia. It stays at rest without a force and only moves when you apply one. When sliding, it stops because of friction, demonstrating that objects resist changes in their state of motion unless acted upon by an external force. This illustrates Newton's First Law clearly.