Pulleys – Simple Machines Activities for Kids

pulleys

In our kids’ STEM class, during our first session on Simple Machines, we covered Inclined Planes and Pulleys.

In this post, I’ll talk a lot about the science of pulleys, and about the grown-up practicalities of how to set up pulley systems that work, but I need to say up-front that pulley play is simply a ton of fun! Kids LOVE playing with pulleys!! They can spend hours engaged in a simple task like lifting toys up to the slide platform, sending them down the slide, and lifting them up again. (Child development theorists call this schema of play “transportation.”)

I’ll start this post with an explanation of the science of pulleys and where to find / how to create a pulley, then we’ll get into fun pulley systems and activities to do with them.

Key concept (the Science of Simple Machines)

A pulley is a wheel that you loop a rope over. The key point of pulleys is that they redirect force. For example, instead of PUSHING a load UP, you can attach it to a rope and pulley above you and PULL DOWN. All pulley systems re-direct force. Some pulley systems make work easier, allowing a worker to use less force to move the object.

A demonstration of pulley-style action:

  1. Tie a rope on something heavy (e.g. a basket of books, a sack of flour, or a 2-liter bottle of soda).
  2. Have a child lift the object off the ground by pulling up on the rope. They may only be able to lift it six inches or so off the ground – partially because it’s heavy, partially because their little arms can only reach so high.
  3. Then have them pick up the object itself and try to lift it high up above their head with their arms. It’s higher now, but wow it feels heavy to push it up.
  4. Then, string the rope up over the back of a chair or over a doorknob and have them pull down on it. It feels easier* to pull the rope down to lift the object than it did to push the object up with their hands. But they can only lift is as high as where the pulley action is happening (e.g. the doorknob).
  5. Then throw a rope over the side of a slide platform (or around a railing on an open staircase: http://handsonaswegrow.com/simple-machines-for-kids-the-pulley/) and put a kid up there to reel it in. Look how high you can lift something when you use this tool!

Where to find a pulley:

Notice that none of those examples use an actual “pulley” from a store – they used a chair or doorknob, a slide platform or a stair railing. You’re getting pulley action just by wrapping a rope around an object and pulling.

You can also rig a “pulley” with other objects you may have:

If you want to buy a basic pulley set for your kids, I think it’s a great investment in a fun toy they can use in a variety of ways for a number of years. The ones we used in class are Block & Tackle Pulley Kit (also available from Magic Cabin Toys). They were good for our purposes, although I strongly recommend using thick utility cord from the hardware store rather than the thin string from the kit, because it will be gentler on children’s hands and less likely to jump off the pulley. The kit came with a nice little book on activities to teach kids about pulleys. I also had a few of  these in a tool boxthat we’ve used. We also considered (but I haven’t tested)Pulleys Discovery Kit and American Educational 7-1607 Pulley Kit. Or, you could get a Clothesline Kit.

We’ve recently inherited some pulleys from a Delta Science Modules kit, but they have very shallow grooves, so aren’t useful for a lot.

img_20170302_101309519

Types of Pulley Systems

Here is an image showing the four main types of pulleys, and here’s a PDF mini-poster you can print of all 6 types of pulley systems I describe.

types-of-pulleys

Pulley Explorations

You can set up a variety of pulley systems… we had them all set up in one class session, but you could also do one each day over a series of classes. Or just set one style up on the playground or in the backyard, and leave it there for months of fun! (See photos of our pulleys at the bottom of the post.)

clothesline pulley

The clothesline. Requires two pulleys. Attach pulleys to anchor points. Take a rope and wrap it around both pulleys, then tie it, making one big loop. Clip things on with clothespins, or tie a basket or other container onto it. Then you pull on either the top or the bottom cord to bring the basket from one end to the other. This is easy for even two year olds to do, and still plenty of fun for elementary aged kids.

  • The rope must be perfectly taut for this to work! If it sags, it falls off of the pulleys. (And if it’s really tight, it’s hard for kids to get it moving.) So, use a rope / cord that won’t stretch out, and expect to spend a while (10-15 minutes?) on tinkering  as you set it up to get it just right.
  • We often set this up at preschooler height, anchored between two chairs. For safety’s sake, be sure to place it somewhere that isn’t a high traffic area that kids run through a lot, and be sure it’s at a height that they won’t be injured if they do run into it.
  • To really engage kids in this activity, make it a message delivery system! Put one end at the writing center, and the other end in the block center and let kids write messages, clip them on, and send them to a friend.

fixed pulley preschool engineering

A fixed pulley. Requires one pulley, and a high place to anchor it. You anchor the pulley, tie a rope onto a bucket, run the rope up over the pulley and back down to the ground. A child standing on the ground pulls down on the loose end of the rope (shown with the green arrow above), and it lifts the basket high up to the pulley. This is the quickest / easiest system to set up.

  • This activity is way more fun if the high anchor is next to somewhere a child can safely stand, like on a slide platform, on a stair landing, in a tree house or the top of a ladder. One child (or a parent) stands on the ground, loads a stuffed animal or other soft toy into the bucket, and sends it up. The other child can send it back down in the basket, or can toss it down or send it down the slide.

basket-on-a-track

A basket on a track. The fixed pulley lifts things straight up from the ground. This is a variant on the fixed pulley, where you can get vertical and horizontal movement by setting up a slanted track for the load to run along as you pull it up. So, first set up the track – shown by the yellow line in the illustration. Run the cord through the handle(s) of a basket or bucket, then tie the cord between a high point and a low point. Make sure the cord is taut, and the basket can slide easily up and down the cord. Then anchor the pulley near the top end of the cord. Tie one end of the rope to the basket handle, throw the rope over the pulley, and leave it hanging down.

  • This is a fun three kid activity. One to load the basket at the bottom of the track. One below the pulley to pull down on the rope to raise the basket, and one up high by the pulley to unload the basket.
  • If the basket is heavy enough, then when the child lets go of the rope, the basket will slide back down to the bottom of the cord. This is a system that takes a lot of tinkering to get it to work right.

moveable pulley kids' science

Moveable pulley. Requires one pulley, a high place to anchor it, and the ability to stand and pull from higher up than the pulley is mounted. Tie a rope up high, run it down through a pulley that has the load hanging on it, then bring the end of the rope up high. Pull the rope up from above the anchor point to bring the load up.

  • For the fixed pulley, you need two kids – one at the bottom to pull the rope, and one at the top to catch the load. With the movable pulley, one kid up top can do both jobs. They run/climb down, load the basket, run/climb up to the top, and pull the load up.

 

compound pulley preschool STEM

Compound pulley. Requires two pulleys – it’s basically a combination of a moveable and a fixed pulley. Tie the rope up high, anchor pulley #2 up high. Then run the rope down through pulley #1 that has a load on it, then up through pulley #2, then down to the ground. You pull down to lift the load up.

Note: If you don’t have two pulleys, you can cheat it. Instead of using pulley #1 with a bucket attached to it, just loop the rope through the handle of the bucket so the rope can run through the handle like it would run through a pulley. (Tie the rope high, run it through the bucket handle, then through a pulley up high.)

block-and-tackle kids' science and engineering

Block and Tackle. There are lots of variant on block and tackle. These illustrations show a simple block and tackle, and a more complex one for lifting heavy loads.

For the simple version, anchor a pulley. Tie the rope to the bottom of it. Run the rope down around pulley #2, then up around pulley #1. Pull down to lift up.

 

Understanding force: In step #4 of our initial demonstration, we said if feels easier* to pull down on a rope that’s looped around something for pulley-like action. This is just a body mechanics sensation – it’s easier to pull down because you can add your body weight in to the motion. But it’s not a scientific measurement of actual total “work” needed. That demo was basically setting up a fixed pulley system, and with a fixed pulley (or basket on a track or clothesline pulley), or you need to use the same amount of force, the pulley just redirects your force. They do not change the amount of force required to move a load.

On a moveable pulley, the work is distributed over two parts of the rope, and the rope is supporting part of the weight. So it takes half as much work to pull it up, but you have to pull twice as much length of rope. The compound pulley distributes the work over multiple pulleys. The more pulleys in your system, the less force you need to use. (And the more rope you have to move.) The block and tackle has multiple loops of rope on multiple pulleys. The more we divide up the work, the less total force is needed. That’s why block and tackles have been used to lift heavy loads for centuries. This Explain that Stuff article does a nice job of explaining the basics of force and pulleys at an adult level.  The Wikipedia article on pulleys has good descriptions of block and tackles.

Other Activities

Math activity: Put weights into each of the baskets. Dominoes? Glass pebbles? Books? What object you choose depends on how strong your baskets, your rope, and your child are. Count how many of that objects you can lift with each type of pulley. Which pulley system helps you do the most work?

Water table: Last year, we built a wishing well from Duplos, thread, and a plastic cup. Note: this requires some specialty Duplo pieces which we got from our Duplo Simple Machines pack. A pulley lifts the bucket up out of the water. This year, we built a bucket elevator (aka rope pump). These were used in the Hanging Gardens of Babylon in 450 BC, and in ancient China. We tied a small plastic “shot” glass to the cord to be the bucket.

Duplo wishing well simple machine pulley img_20160923_142128707 img_20160923_142145005  

Challenge Activity – Build a Flagpole System. We put out straws, binder clips, spools, bobbins, string, and clay, and encouraged children to try making a flag pole. We also offered a couple samples we had assembled. This project was over the head of most of our preschool aged kids, but our older kids and parents had fun with the challenge.

Art project: Flagpoles use pulley systems to raise the flag. We had the children decorate paper flags with markers. Next to this station, we put posters showing the flags of all 50 states, and most countries, to serve as inspiration for the activity.

Here’s a fun craft to make with recyclables: build a winch system: http://littlebinsforlittlehands.com/

Circle Time

For a pulleys-only class, you can do a demonstration exactly as described at the top of this post to show the mechanics of pulleys, then demo how each system works, and what the advantages are of each system

Or… we combine this topic with inclined planes, so here’s our circle time plan: We set up a ramp (inclined plane) using a long plank propped up on a step ladder. At the bottom of the plank, we set a basket full of two stuffed elephants. We tied a rope on the basket, ran it through a pulley attached to the step ladder, and back down. (A fixed pulley.) We had the kids haul on the rope to pull the elephants up the slide. It was HARD work! They had to learn how to brace their bodies to pull hard (a good large motor skill to learn!) Some kids would just pull on the rope and keep backing up further and further. Some understood how to pull hand over hand, so they could stand in one place and alternate hands to pull with. (Pulling hand over hand is also a great large motor skill to learn.) They were putting so much force into their pulling that an adult had to brace the ladder so it wouldn’t tip over.

Then, while I read the day’s book (Raising a Bag of Toys: Pulley vs. Inclined Plane), we acted out the story with our slide, which illustrated the different advantages of pulleys and inclined planes to raise a toy up to the slide platform.

Before closing circle, my co-teacher re-rigged the pulley system so it was a block and tackle attached to the basket of elephants. After the story, we had them all try pulling the elephants up again. It was SO MUCH EASIER for the kids to do. (And no need for an adult to brace the ladder.) This was a fabulous hands-on experience that really helped them appreciate the power of the block and tackle.

Books, Songs, and Videos

Song: I didn’t really find a song that was good for this age group to sing… but for the entertainment and amusement of adults or older kids, check out “The Sick Note / Why Paddy’s Not at Work Today”: www.youtube.com/watch?v=iA5RGI3zn20

Books: Here’s a full post on all the kids’ books about simple machines: https://inventorsoftomorrow.com/2017/03/01/books-about-simple-machines/

Videos about pulleys: www.youtube.com/watch?v=9T7tGosXM58 and www.youtube.com/watch?v=LiarGb_LK10

For a great collection of pulley activities for kids, including recommended books, click here: http://iijuan12.hubpages.com/hub/gears-and-pulleys-simple-machines-lesson-plan. Here are a couple fun posts about how parents added pulley play to their backyards for hours or years of fun for their kids: http://handmadekidsart.com/backyard-pulley-engineering-kids/; http://happyhooligans.ca/a-bucket-and-a-rope/; and http://littlebinsforlittlehands.com/homemade-outdoor-pulley-play-idea-simple-machines/

Photos of Pulleys in Action

Here are pictures from class. I apologize for their quality. It’s hard to get a good picture of pulleys and ropes!

Clotheline. Here’s the top of the clothesline (above) and the top of the basket on a track (below) where they attached to the slide platform. (Click on any image to see a larger image.)

top

Fixed. The pulley is tied onto the slide platform. Child at the bottom loads a stuffed animal and pulls it up to their buddy.

Basket on a Track. View from the bottom of the track, and the top. The brown twine is the track, the yellow rope runs over the pulley.

  

Compound:

img_20160924_142007223Here’s one compound “pulley” system, using the bucket handle as the movable “pulley” and a spool for the fixed “pulley”

 

For this compound system, the rope is tied onto frame, then loops down through a movable pulley, up through a fixed pulley, back down through the movable pulley, up over the top of the frame, then ties to the leg of the frame. If kids pull where the post-it is, it lifts the very heavy bucket up high.

The peg board offered a build-your-own pulley system, where kids could re-arrange the pulleys and the ropes to test multiple paths. In the photo shown, the cord is fixed on the left, then runs over a red fixed pulley, down to a silver movable pulley tied to a pouch full of glass weights, then up and over a red fixed pulley then tied to a second pouch. Kids could load pouch #2 with stones until it was heavy enough to pull pouch #1 up. This was a great idea but harder in practice as the cord was very prone to slipping off the pulleys. With adult assistance, it was a fun activity.

Here’s our block and tackle system, set up on a ramp.

img_20160924_142103665_hdr img_20160924_142051759

Note: All the activities described in my posts are from Family Inventor’s Lab, a parent-child cooperative class in Bellevue, WA. We are a play-based, STEM focused class for preschool through early elementary (kids age 3 – 7). We do a wide variety of fun, hands-on activities to learn about Science, Tools, Engineering, Nature, and Art. We also sing songs and read stories. Most of our activities are cheap, easy, and use everyday materials that most families would have in their homes (or their recycle bins!), so that our activities are appropriate for classroom teachers, parents who homeschool, or after school programs.

Here are our other lessons for Simple Machines: Overview of Simple MachinesInclined PlaneLeverWedgeScrewWheel and Axle.

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