CHAPTER 3: NEWTON'S LAWS OF MOTION

Sir Isaac Newton's Three Laws of Motion are the bedrock of classical physics. They describe the relationship between a body and the forces acting upon it, and its motion in response to those forces. From a ball rolling on the ground to a rocket launching into space, everything obeys these laws. Master them, and you master the mechanics of the universe.

3.1 NEWTON'S FIRST LAW: THE LAW OF INERTIA

3.1.1 Statement of the First Law

"Every object continues in its state of rest or of uniform motion in a straight line unless acted upon by an external unbalanced force."

This means that objects are lazy. They don't want to change what they're doing. If they're stationary, they want to stay stationary. If they're moving, they want to keep moving at the same speed and in the same direction.

3.1.2 Inertia

Inertia is the property of an object to resist any change in its state of motion. It is not a force; it is a resistance to a change in motion.

• Mass as a Measure of Inertia: The greater the mass of an object, the greater its inertia. It is harder to start a heavy object moving, and harder to stop it once it's moving.
• Examples of Inertia:
  • When a car suddenly stops, your body lurches forward because it wants to keep moving.
  • When a car suddenly starts moving, your body jerks backward because it wants to stay at rest.