Types of Friction

Imagine you're trying to move a heavy box across the floor. You push and push, but at first, it doesn’t budge.

That’s static friction—the force that keeps the box stuck in place. It acts between the box and the floor, resisting the start of motion.

You push harder, and finally, the box starts sliding. Now, sliding friction takes over.

This type of friction acts while the box is moving. It still resists motion, but not as strongly as static friction did. That’s why it’s usually harder to start moving something than to keep it going.

But what if you place the box on a dolly?

Suddenly, it moves much more easily. That’s because of rolling friction.

Rolling friction is the weakest of the three. It acts when objects roll over a surface.

Wheels, as seen on suitcases or carts, make it easier to move by reducing resistance through rolling friction.

So, friction acts differently depending on whether an object is static, sliding, or rolling.