Inertia and the First Law


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The Law of Inertia

Newton's First Law says that any object made of matter has the property that it resists accelerations. The name of this property is inertia - inertia is the property of matter that causes objects to not "want to" accelerate. It is important to understand that inertia is not a force - inertia does not push an object along. Inertia is a property of matter, like color, density, etc.

Since Newton's First Law says "Objects made of matter have inertia.", it is often called the Law of Inertia.

The second thing (remember the first paragraph?) that is important to remember about inertia is that all objects made of matter obey Newton's First Law - regardless of how much inertia they have. Some objects resist accelerating more than others. It is easy to accelerate a dust mote - the lightest draft will do it, but it is another thing to accelerate an SUV! Even though the dust mote and the SUV have different amounts of inertia, they both obey Newton's First Law in the same way. Newton's First Law does not depend on how much inertia an object has - all objects made of matter have inertia, and they all obey Newton's First Law. In a little while, when we get into Newton's Second Law, the amount of inertia an object has will become important - but not now.

last update November 27, 2002 by JL Stanbrough