Inertia is defined as which of the following?

• A. Inertia is the rate at which energy is transferred.
• B. Inertia is the tendency of objects to resist a change in motion.
• C. Inertia is the force that stops motion.
• D. Inertia is the energy of motion.

Answer: (B)

Inertia is the tendency of objects to resist a change in motion. This means an object at rest tends to stay at rest, and a moving object tends to keep moving in the same direction and at the same speed unless an external force acts on it. Mass reflects how much inertia an object has—the larger the mass, the greater the resistance to changes in motion. For example, a heavy cart is harder to start or stop than a light one. In space, where there’s no friction, a moving object continues moving in a straight line unless something pushes or pulls on it. The other statements describe energy transfer, a force that stops motion, or energy of motion, which aren’t what inertia means.