**Herong's Notes on Physics** - Version 3.21, by Dr. Herong Yang

Newton's First Law of Motion

This section introduces Newton's First Law of Motion - If the net force acting on an object is zero, then the velocity of the object is constant.

Newton's First Law of Motion - If the net force acting on an object is zero, then the velocity of the object is constant.

Newton's first law of motion can also be stated as: An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

If a running car lost control on a curved road, it will continue to run in straight line until an external object like a tree to apply an unbalanced force on it.

Newton's first law of motion is also called the "Law of Inertia", which can be stated as: Every object has a property called "inertia" that gives the object a tendency to keep its current state of motion.

*Last update: 2014.*

Table of Contents

Introducion of Frame of Reference

Falling Ball in Earth Frame of Reference

Falling Ball in Elevator Frame of Reference

Introduction of Special Relativity

Time Dilation in Special Relativity

Length Contraction in Special Relativity

The Relativity of Simultaneity