What is inertia?

What is inertia?

• A. The resistance to changes in motion
• B. The rate of change of velocity
• C. The force needed to stop an object
• D. The energy possessed by an object

Answer: (A)

Inertia is the tendency of an object to resist changes in its motion. It’s why a stationary object stays put until a force pushes it, and a moving object keeps moving in a straight line unless a force slows it down or speeds it up. The amount of inertia depends on mass: more mass means more resistance to changing motion, so you have to apply a greater force to start or stop it. That’s why the rate of change of velocity isn’t inertia—it's acceleration, which measures how quickly velocity changes. The force needed to stop an object describes the external force you must apply, not the resistance itself. And the energy an object has is its kinetic or potential energy, not inertia.

Inertia is the tendency of an object to resist changes in its motion. It’s why a stationary object stays put until a force pushes it, and a moving object keeps moving in a straight line unless a force slows it down or speeds it up. The amount of inertia depends on mass: more mass means more resistance to changing motion, so you have to apply a greater force to start or stop it.

That’s why the rate of change of velocity isn’t inertia—it's acceleration, which measures how quickly velocity changes. The force needed to stop an object describes the external force you must apply, not the resistance itself. And the energy an object has is its kinetic or potential energy, not inertia.