What is Inertia?

What is Inertia?

• A. A body at rest will remain at rest and a body in motion will continue in motion in a straight line at the same speed unless enacted upon by an external force
• B. Energy of motion
• C. A force resisting motion
• D. The rate of acceleration

Answer: (A)

Inertia is the tendency of matter to resist changes in its motion. An object at rest tends to stay at rest, and an object in motion tends to continue moving in a straight line at the same speed unless an external force acts on it. This is Newton's first law and explains why, for example, a parked car stays put until someone pushes or starts it, and a moving vehicle would keep going straight at the same speed unless friction or a collision slows it down. This idea is not about energy of motion (that’s kinetic energy), nor about a force that resists motion (that would be friction), nor about how quickly velocity changes (that’s acceleration). Inertia is the inherent property of matter that makes changes in motion require a force. Mass influences inertia—the more mass, the greater the resistance to changes in motion.

Inertia is the tendency of matter to resist changes in its motion. An object at rest tends to stay at rest, and an object in motion tends to continue moving in a straight line at the same speed unless an external force acts on it. This is Newton's first law and explains why, for example, a parked car stays put until someone pushes or starts it, and a moving vehicle would keep going straight at the same speed unless friction or a collision slows it down.

This idea is not about energy of motion (that’s kinetic energy), nor about a force that resists motion (that would be friction), nor about how quickly velocity changes (that’s acceleration). Inertia is the inherent property of matter that makes changes in motion require a force. Mass influences inertia—the more mass, the greater the resistance to changes in motion.