Here's why:
* Inertia is the tendency of an object to resist changes in its motion. This means it resists both starting to move and stopping once it's moving.
* Inertia is a property of mass. The more mass an object has, the more inertia it has.
* Inertia is not related to an object's current motion. Whether an object is at rest or in motion, its inertia remains the same.
Think of it this way:
Imagine a bowling ball sitting still on the ground. It takes effort to get it moving, right? That effort is required because of the bowling ball's inertia. If the bowling ball were already rolling, it would still take effort to stop it, again because of its inertia.
In conclusion:
* Inertia is an intrinsic property of an object.
* A non-moving object has the same inertia as a moving object with the same mass.
* Inertia is the reason why it takes force to start or stop an object.
