Inertia is the tendency of an object to stay at rest or stay in motion. What does inertia depend upon?

• A. Temperature
• B. Volume
• C. Mass
• D. Color

Answer: (C)

Inertia is the resistance to a change in motion, and that resistance depends on how much matter there is—the mass. The more mass an object has, the harder it is to start moving from rest or to slow down and stop when it’s already moving. That’s why a heavy object, like a car, takes more push or force to accelerate than a lighter object, like a bicycle, for the same push. Temperature, volume, or color don’t set this resistance: temperature can affect how surfaces interact but not the intrinsic pushback against changing motion, volume isn’t the measure of how much matter you have, and color has no effect on motion at all.