Inertia is a measure of an object's resistance to changes in motion. It depends solely on the object's mass, not its speed.

Therefore, an object with more mass has more inertia, regardless of its speed.

Here's why:

* Inertia is about resistance to acceleration: A heavier object needs more force to get it moving or to stop it once it's moving. This is because its inertia is greater.

* Speed doesn't affect mass: A fast-moving car might be hard to stop because of its momentum, but that's not the same as inertia. Its inertia is determined by its mass, not its speed.

Think of it this way:

* A massive truck parked at a stoplight has more inertia than a tiny sports car going down the highway. The truck requires a lot more force to get moving or to stop.

So, the key takeaway is: mass determines inertia, not speed.