Newton's First Law: Introduction

Motion draws our attention. Motion itself can be beautiful, causing us to marvel at the forces needed to create spectacular sights, such as that of a dolphin jumping out of the water, the flight of a bird, or the orbit of a satellite. The study of motion is kinematics, but kinematics only describes the way objects move—their velocity and acceler...

Before Galileo and Newton, scientists held a 2000-year-old belief that objects have a natural tendency to come to rest if left alone.

Also, a constant force is necessary to keep them moving.

Galileo disproved this idea with a thought experiment using a bronze ball that is rolled over smooth double inclined planes.

A ball rol...