Simple Machines: The Pulley

Hi, I'm Jared. Welcome to FunScienceDemos. In other videos we talk about

simple

machines

and how

simple

machines

make our work easier. Today we're going to talk about another simple machine called a

pulley

, and that's a

pulley

, so let's take a look at our setup. I weigh a thousand grams and I have a spring scale. Now, if I put my spring scale on my weight and lift it up, it will weigh a thousand grams. We can get closer and take a closer look to see that it weighs a thousand grams. Then our spring scale showed us that this thousand gram weight is actually a thousand grams, but we said that simple machines make our work easier.

We also said that this pulley is a simple machine, so how do we show you that this pulley makes our work easier? Well, we're going to run this rope through our pulley, attach it to our weight, and attach the other end to our spring scale, and now we can see if our simple machine, our pulley, really makes the job easier. Now it's time to see our pulley in action. I'm going to pull down on the spring scale, and when I pull down, the weight should go up, and let's see if this pulley has made our job easier by taking a closer look at our spring scale.

Here we go. I pull down, the weight goes up and now let's zoom in and take a closer look at our spring scale to see if our pulley makes our job easier. So our weight is not in contact with the ground, and when we look at our spring scale it is just that: about a thousand grams. But wait a second, that hasn't really made our job much easier, so let's change this setting and use this pulley differently to see how it works. To do that, I'm going to remove the pulley, the scale, and the weight, and I'm going to attach the pulley to my weight.

Now I'm going to run my rope or my cord, and tie my rope to a fixed point on top of the weight, and then I'm going to place my spring scale. It seems that I have invested everything. Instead of the pulley being up, it's now down, and we're going to try lifting this weight with the pulley down and see what happens on our spring scale. Let's zoom in and take a closer look so you can see if our job really is made easier by using our pulley differently. Right now our spring scale reads zero grams, down here it reads a thousand.

Watch closely what happens to our spring scale when I get up. I get up, the weight is off the table, but my spring scale didn't go down to a thousand. Let's get closer and take a closer look. So we zoom in and we can see that our spring scale is right at 500 grams. I would say that this pulley has made our job easier. In our last setup it took about a thousand grams, but with this setup, because we use our pulley differently, we are at 500 grams. If one pulley can make our job easier, it makes me think, I wonder if two pulleys can make our job even easier.

What do you think will happen? Now we have two pulleys set up and working together. I have a rope tied to my top pulley that goes down around my bottom pulley, up over this pulley and now I have my spring scale tied to it. Now I can go down and see if this really makes our job easier. Remember that when I had a pulley at the bottom it weighed 500 grams, what do you think will happen when I pull it down? How much do you think our spring scale will read? We'll lower our spring ladder, get closer and take a closer look so you can see what's going on.

I pulled down, my weight is not touching the ground and now we are going to approach our spring scale. You can see that my spring scale is at 500 grams, so did adding another pulley really make a big difference? It didn't, but remember that adding a pulley didn't make much difference, but then we used that pulley differently, so I'm wondering if we add a third pulley but use it a little differently, if that will make our job easier, so let us deal with it. that. So now we have one, two, three pulleys working together and we try to follow this because I'm going to show you how we set this up.

So I have a rope tied to my weight of a thousand grams, remember that's a thousand grams. The rope goes up over the first pulley, down the bottom of the second pulley, back up over this third pulley and now I have my spring scale so we can make sure to check if all of these pulleys really work together It makes our job easier. Remember when we had two pulleys working together? It was about five hundred grams, it made our job easier. What will it be when we have three pulleys working together? Let's go down and see if our spring ladder is working and then get closer and take a closer look.

I pull down the spring scale, my weight goes up and now let's zoom in to see what our spring scale says. Check this out: Our spring scale shows 300 grams. Three pulleys working together (required a thousand grams of weight) and now I'm only pulling 300 grams. I would say our job is actually easier. I wonder what would happen if we put four pulleys, or five pulleys, or six pulleys, or seven pulleys all together and made them work together. It would be very complicated to show you, and in fact, scientists have designed a pulley system in which all of these pulleys are very close together.

It is called a block and tackle and is made for easy lifting. It makes the work easier. Simple machines, such as pulleys, make the job easier. Pulleys are simple machines and they really are all around us. Cars use pulleys, boats use pulleys, cranes use pulleys, look around and see if you can find pulleys, but sometimes you may just have to look up to find that pulley. If you want to learn more about pulleys and simple machines, check out some of our links in the video description. Science is great, especially when it makes our jobs easier. Thanks for watching.