inertia
Inertia is the tendency of an object to resist a change in its motion. All objects have inertia, whether they are stationary or moving. Inertia explains Newtons first law of motion, which states that an object at rest will remain at rest and an object in motion will stay in motion unless it is acted on by an unbalanced force. Thats why Newtons first law of motion is sometimes called the law of inertia. You can see an animation of inertia at this URL:.