Inertia is a concept from Newton's First Law of Motion.

It says:

• An object that is not moving will stay still.
• An object that is moving will keep moving until something else makes it stop.

Mass and Inertia

The more massive an object is, the more it wants to keep doing what it's doing.

For example:

• A car (which weighs about 1,500 kg) is harder to stop than a bicycle (which weighs about 15 kg).

Everyday Examples

• If you push a shopping cart, it will keep rolling until friction or something else stops it.

• Seat belts are really important in cars because they help keep you safe during sudden stops. They work against inertia.

When we understand inertia, we see why it's important to drive carefully. It helps keep everyone safe on the road.