Air resistance and friction

How do you stop a moving object?

No matter how much force you give an object to make it move, when you stop giving the force, the object will start to slow down.

This is because two things slowly reduce the speed of moving objects. These things are air resistance and friction.

Air resistance is air pushing against a moving object. The air pushes on the object as the air gets out of the way to let the object through. If you've ever been on a rollercoaster, or cycled fast down hill, you might have felt this air resistance as a wind on your face.

Friction is the rubbing that happens between an object and the surface it moves over. Slide your hand over any surface (for example, your desk) and you will feel a little resistance to your movement and your hand will get hotter. This is friction. It happens because the surfaces kind of stick together a little.

Rub your hands together and you will feel the friction as heat.