MASS AND INERTIA: NEWTON'S FIRST LAW
An object at rest tends to stay at rest and an object in motion tends to stay in
motion in a straight line at a constant speed. The above is a statement of Newton's first
law, and it expresses what we mean when we say that an object has inertia. Inertia is that
property of matter which causes matter to resist change in motion. Mass (one of the four
basic measurements) is a measure of inertia.