Objects don’t start or stop their motion unless forced to do so by something. This rule applies to all objects in the universe. Scientists call this inertia. Inertia is the quality an object has when it resists movement or a change in movement.

1. What is required to force something to move?
2. What is required to force something to stop moving?
3. Do you think it is easier to force a less massive (lighter) object to start or stop moving or a more massive (heavier) one?
4. Do you think that mass, whether the object is light or heavy, resists change of motion?