Here's why:

* Inertia: Inertia is the tendency of an object to resist changes in its motion. This means an object at rest wants to stay at rest, and an object in motion wants to stay in motion at a constant speed and direction.

* Mass: Mass is a fundamental property of matter that quantifies the amount of matter in an object.

* Relationship: The more mass an object has, the greater its inertia. This means it takes more force to get the object moving, and more force to stop it once it's in motion.

Example:

* A bowling ball has a large mass and therefore a large inertia. It takes a lot of force to make it move and a lot of force to stop it.

* A feather has a very small mass and therefore a very small inertia. It takes very little force to get it moving and very little force to stop it.

Key Points:

* Inertia is not the same as weight. Weight is the force of gravity acting on an object's mass.

* Mass is a scalar quantity, meaning it only has magnitude (amount).

* Inertia is a property of all objects, regardless of their state of motion.

Let me know if you have any other questions!