(Intro)

Today is a really exciting day at the fort. We're going to move my brand new telescope into the fort's observatory, and I can't wait to use it tonight. But, wow, is this telescope heavy, and we have to get it all the way up there. I can lift the box, but I don't think I can carry it all the way up the stairs and I'm not going to try to move it up the ladder. So, we're going to have to think of another way to get it up there. 

[Squeaking] Right on, Squeaks! Lately, we've been solving a lot of problems around the fort using simple machines, things that make it easier for us to do work like ramps and levers. Because we use these simple machines, we're able to do things much more easily, like when we move boxes of books up a ramp and used a lever to help us turn big rocks over during our bug safari.

And, I know a simple machine that can help us with this job. This one's called a pulley. Pulleys are used to help lift heavy things. The thing that's being lifted is called the load, and when we attach the pulley's rope to the load and pull, the load goes up. A pulley has two main parts, a string or a rope and a wheel. The wheel on the pulley is special, because it has a groove that goes all the way around it. The rope fits into the groove just like this. So, if I try to lift this box up over my head by just using my arms, oof, that's a lot of work, but if I attach the box to a pulley and then pull on the rope, the job becomes much easier.

So, let's see how a pulley can help us with our telescope problem. First, we need to attach a pulley and a rope above the window of the fort. Next, we'll attach one end of the rope to our load, which is the telescope box, and the junior scientist will get ready to bring the box in through the window. Alright, is everyone ready? Ready, Squeaks? [Squeaking] And, pull! Oh, it's working! Take a close look at what's happening here. As Squeaks pulls down, the rope turns the wheel, and the telescope box moves up; all the way up to the window where they can grab it, and pull it into safety. Ha! They did it, and it was a lot easier than trying to carry that heavy box up the stairs. 

Now, pulleys can help us do some pretty big jobs. For example, the cranes that we use to build skyscrapers and the elevators that take us between the floors of those skyscrapers work because of pulleys. But, pulleys help us do smaller jobs, too. Did you know you use a pulley when you open or close the window blinds and curtains in your house? And, Squeaks and I use a pulley every time we raise the flag on our forts flagpole. First, we clip the flag onto the rope. Then, when we pull down on the rope, it makes the pulley's wheel turn and it raises the flag high into the sky.

And, speaking of the sky, it's time for me to set up my new telescope. Thanks for helping us today! We'd like to give a big thanks to Google Making Science for helping us make this episode. Do you have a question about machines, telescopes, or anything else at all? Ask a grownup for help, and leave us a comment below or send as an email to kids@thescishow.com, and we'll see you next time.