Swing sets! Slides! Everyone has a favorite at the playground, but did you know that when you're soaring on the swings or sliding down the slide, you're taking part in some seriously cool science?

It's true! Playgrounds are awesome places to learn about forces! Forces are the pushes and pulls that happen to objects, including us, every minute of every day.

Forces help planes get off the ground when they take off, and they help cars stop safely at traffic lights. You probably already know the name of one really important force, gravity.

That's the force that pulls us, and everything else around us, toward the Earth. When you throw a ball in the air, gravity is the force that makes it fall back to the ground.

Now, gravity and other forces all work by certain rules all the time, and a great scientist, Isaac Newton, spent a lot of time studying forces and how they work, and he discovered some of the most important rules about what happens to things when forces act on them.

One rule is that something that's sitting still will stay still, unless a force makes it move, and something that's moving will keep on moving, unless a force makes it stop.

So basically, forces are always making things move, or keeping them from moving. Want to see for yourself? Check out the swings.

A swing in a playground isn't going to move, unless you or something else puts a force on it. When a friend pushes you on a swing, he's putting a force on you, which makes you and the swing move.

Or maybe you're swinging by yourself. When you pump your legs, that movement puts a force on the swing too. But unless you, or your friend, or something else puts a force on the swing, it's just gonna sit there - that's part of what Newton figured out.

Now, remember the second part of Newton's rule? It says that when something is moving, it'll keep moving, unless something makes it stop. So does that mean that once you get going on the swing, you'll keep swinging for ever?

Well, I gotta say that sounds pretty awesome, but it can't happen. Because when you're on the swings, there are forces around you that will make you stop moving.

One of the main forces is friction. Friction is the force that happens when two things rub against each other, and I bet you've seen how it works before. Imagine you've been swinging for a while, pumping your legs until you got good and high, and then you stop pumping.

As you keep swinging back and forth, there's a lot of friction between you and the air, and there's also friction where the swing's chains meet the top of the swing set. Together, all of this friction makes you slow down, and if you wait long enough, you'll come to a complete stop.

You can even create more friction. If you drag your feet on the ground, you can help yourself stop faster. Now, do you know another place in the playground where friction is at work? The slide.

Gravity pulls you down the slide, but friction between you and the slide slows you down, so it lets you go at a fun but not scary speed. But if you've ever been on a water slide, the reason you go down so much faster on a water slide is because water reduces, or takes away, some of the friction between you and the slide. Good thing there's a nice big pool of water for you to land in at the bottom.

So now you know how forces work at the playground, and everywhere else. Now go outside and get your body in motion and see what forces you discover!

Thanks for joining me on SciShow Kids! If there's something that you would like to learn more about, let us know by leaving a comment or emailing us at kids@thescishow.com ! Thanks guys, and we'll see you next time at the fort!