Gears and Pulleys Simple Machines Lesson
This is part 4 of a 6 part hands-on unit on inventions and simple machines. Build and test pulleys, play pulley tug-of-war, find out how a clock works, and more! My lessons are geared toward 3rd-4th grade level children and their siblings. These are lessons I created to do with a weekly homeschool co-op. We meet each week for 2 1/2 hours and have 17 children between the ages of 1-13. Use these fun lessons with your classroom, family, after school program, or co-op!
Gears and Can Openers
1. Pray. Read and discuss Luke 5:17-26 and Acts 9:22-28. A pulley is a wheel with a groove for a rope that is used for lifting, lowering, or moving objects. How might pulleys have been used in both of these instances?
2. Review simple machines. Introduce gears, which are wheels with teeth.
3. *Wash hands.* Divide children into groups of 3-4. Give each group a can opener, a can, napkins, and forks.
-First have the children take turns twisting the handle of the can opener and watching the gears.
-Then let the children take turns twisting the handle to open the can. *Point out how the gears move in opposite directions on the can opener which causes the can to move around the blades.
-Allow each child to use their fork to stab piece of fruit and eat it over the napkin.
-As the children eat their fruit, ask, “Can anyone notice other simple machines?” (A can opener uses screw, a lever, a wedge, and a wheel and axle. The wedge is found on the cutter, the lever is the handle, and the screw is the device that holds the can opener together. The wheel and axle attaches the cutter to the opener. They all work together to make opening a can much easier!)
YOU WILL NEED: 1 napkin & fork per child & items brought by families: can openers and cans of fruit
4. Have children sit on the floor around the bicycle. Who owns a bicycle? Who likes to ride their bike? Is it easier to run a mile or bike a mile? Would it be faster to run a mile or bike a mile? Why? A bicycle uses simple machines to make work easier! One of those simple machines is a variation of a wheel: a gear.
-Turn a bicycle upside down to observe its gears. Point out where the air valve is on the back tire. Now turn the pedal half way. Did the back wheel turn the same distance (half way around)? (Yes.)
-Now move the pedal one full rotation. Did the wheel move the same distance (half way around)? (Yes)
-How does moving the pedal cause the tire to move? (the gears and chain) This back gear is called the back derailleur or sprocket. The front one is called the front derailleur or sprocket. (Have the children repeat those words.)
-When I pushed the pedal, do you think both the front and back derailleurs made the same number of rotations, meaning they both turned around the same number of times? Who thinks yes? Who thinks no?
-Let’s test your hypothesis. (Put a piece of tape on each derailleur.) I’m going to turn the pedal slowly around one time. I want everyone sitting on my right to count the number of times the front derailleur/ sprocket rotates around one circle. I need everyone on my left to keep an eye on the back derailleur/ sprocket rotates around.
-What is the ratio of turns between the front sprocket and the back sprocket?
-Hmm. Now let’s count how many teeth each sprocket has. Before we count, let’s make a hypothesis. Who thinks they will be the same ratio? [Mom Helper], please work with the kids on my left to count the teeth on the back derailleur/sprocket while I work with the kids on my right to count the teeth on the front derailleur/sprocket.
-Which one has more teeth? What is the ratio?
-Did you know that different bikes have different numbers of teeth on them? How do you think this might affect your speed? (If you want to get into more detail about this you can watch this video and try to summarize it – but you do not need to unless you really want to.)
- What other simple machines do you see on your bike? (lever where gears change, kick stand is lever, wheels)
- Before gears were created, bicycles had very large front wheels. (Show a picture of one.) They were called penny farthings and they were faster than the bicycles we have now with 2 of the same size wheels. Why do you think that is? (Allow children to answer.) When I turn this pedal around one time, my bicycle moves the distance of one tire, which is about 7 feet on this bicycle. If I had a bigger tire, my bicycle would move that much further with one rotation of the pedal.
-Why do you think we don’t use those types of bikes anymore? (They required more effort and balance. They were also quite dangerous. If you flew off, you would hit your head -- which could sometimes be fatal.)
YOU WILL NEED: 2 pieces of masking tape or 2 stickers, picture of an old bicycle (penny farthings or velocipedes) [printed from the Internet, from a book, or on your laptop] & a bicycle
6. (If not limited by time) Take off the backs of 2 clocks to observe the gears. Divide the children into 2 groups and give each group a clock. What is the ratio of teeth in the gears connecting the second hand to the minute hand? The minute hand to the hour hand?
-Ask children if they can think of any other gears they might use. Ask them what they have learned about gears.
YOU WILL NEED: at least 2 clocks with the backs taken off
6. Now let’s learn about the last type of simple machine: the pulley. A pulley is a wheel with a groove for a rope that is used for lifting, lowering, or moving objects.
-We’ve mentioned Archimedes a few times. He was an Ancient Greek mathematician and inventor and used a number of simple machines to do amazing time. What is his famous quote about levers? (“Give me a lever long enough and a fulcrum on which to place it, and I shall move the world.”) His relative, King Hieron, said, “Prove it!” Archimedes did! He told King Hieron to get his biggest ship and fill it with its usual amount of freight and number of passengers. He then pulled the ship toward himself using only one hand! Do you know how he did it? He used a pulley system! Let’s learn about this last simple machine, the pulley.
-Read "Pulleys to the Rescue" by Sharon Thales or "Pull, Lift, and Lower: A Book About Pulleys" (Amazing Science: Simple Machines).
YOU WILL NEED: book: "Pulleys to the Rescue" by Sharon Thales or "Pull, Lift, and Lower: A Book About Pulleys" (Amazing Science: Simple Machines)
This is the book we read for activity 6 when I taught to a younger class. It is great because it has illustrations rather than photographs, so it holds the interest of my 3 year old while teaching my 8 year old what he needs to learn.
7. Divide children into pairs. Give each pair 2 napkin holders or curtain rings and 20 feet of string. Have each pair attach a long length of string to one napkin holder/curtain ring with a tight knot and pass the end of the string through the other ring. Have their partner (Child 2) hold the 2 rings about 3 feet apart. Child 1 will stand opposite child 2 and pull the loose end of the string about 3 feet down from the second ring (the one that's not knotted to the string).
-Child 1 will try to bring the 2 rings together while child 2 tries to keep them apart. Who succeeded? Was it easy or hard?
-Now switch roles and try again. Were the results the same?
-Next have them pass the string in and out of the rings 5 times. Do they think it will be easier or harder to pull the rings together this time? Repeat the experiment with each child having a chance to hold the rings the same distance apart as before.
-What happened? Who has super strength? Why?
YOU WILL NEED PER PAIR OF CHILDREN: 2 sturdy napkin holders or curtain rod rings and 20 feet of sturdy yarn/string
Pulley Tug of War
8. Now divide children into 2 groups and go outside. Give each group 2 broomsticks or similar strong sticks and rope.
-Have each group tie one end of the rope to one broom handle. Have the other 4 people stand facing each other about 2.5 feet apart. Have each person hold part of the broom handle in front so that the brooms are about 2 feet apart. The brooms will be the wheels of your pulley.
- Have each group decide who their strongest person is. Have the "strongest" person wrap the rope around the broom handles two times.
-While facing the other 4 children, have the "strongest" person hold on to the free end of the rope and try to pull the rest of the group toward himself/herself while they pull the brooms away from each other.
-What happened? Could you do it? (No.)
-Keeping the last experiment in mind, can anyone think of a way our "strongest" person could pull everyone? (Wrap the rope around the handles 2 more times.) Now have the "strongest" person try to pull the group while they try to pull the brooms away.
-What happened? (When you wrapped the rope around 2 more times, you decreased the effort needed to pull the load. By increasing the distance over which the force was applied, it took less effort to move the load. What you just made is called a movable pulley. It doesn't change the direction of the force. The load moved in the direction you pulled.)
(If the above directions don’t make sense, you can instead follow these directions.)
YOU WILL NEED: 2 long ropes and 4 wooden sticks (such as broom or mop handles)
Devise Your Own Pulley System
13. Build Your Own Pulley. Divide children into groups of 3-4.
-Give each group a wooden broom, rope, and a gallon jug. Have 2 children hold down the ends of the broomstick between two tables. Have them experiment to find the easiest way to lift the jug.
-If children need assistance making a movable pulley, lead them in tying the rope to the broom handle and looping it around a few times, looping the rope through the jug handle, and lifting by the free end of the rope with the weight in the middle.
-Make sure that everyone eventually determines that the more times the rope is looped through the jug and over the broom handle, the less effort needed.
pulleys change the direction of force used and allow people to lift things to places out of reach
YOU WILL NEED: 2 ropes, 4 gallon jugs (milk/tea/water) filled with water, 4 wooden brooms/mops
Pulleys Share Half the Load
10. Demonstrate what happened. Get 3 volunteers. Have one child hold 4 heavy books. Have the second child take 1/2 of the load (i.e. 2 books). Then have the third child take 1/2 of the second child's load (i.e. 1 book.) This is really 1/4 of the original load. Just as the first pulley took 1/2 of the load, the 2nd pulley took 1/2 of a half or 1/4 of the load. Each time you wrapped the rope around the broom handle and milk jug, it was like you were adding an additional pulley.
-In a moment we are going to learn about simple pulleys, which have one pulley system, and compound pulleys, which have more than one. Is it easier to do a job when you have 1 or more than one pulley? (more than one – the more pulleys = the less force is needed). Wrap a rope around the handle of one of the full gallon jugs and have 1 volunteer hold it up by the rope. This is what it is like with a single, fixed pulley. Then have another volunteer come up. Have them each hold an end of the rope so that they are now sharing the weight. This is what happens when you add another pulley. The movable pulley is sharing one-half of the load.
YOU WILL NEED: 4 heavy books and rope and filled gallon jug (used in above activity)
11. (The favorite activity!) Play with pulleys. Ahead of time we (i.e. my husband) devised two pulley systems. For the simple system he attached a wood screw with hook (rated for 250 pounds) to a solid cross beam (a tree limb). He hooked on a single eye pulley and then ran a climbing rope through the single eye. He attached a thick, straight branch to each end of the rope to act as handles. We had our youngest son hold on to one side and then each person got to try to pull him off the ground. They still have to pull his entire weight.
For the compound pulley my husband attached a wood screw with hook (rated for 250 pounds) to another solid cross beam (a tree limb). He hooked on a single eye pulley. He tied one end of the rope to the support beam/branch, ran the rope through the bottom of the single eye pulley (though a double eye pulley would be better) and ran the rope up to the top of the single eye pulley. He attached a thick, straight branch to each end of the rope to act as handles. The children then each take turns lifting my youngest son using this system. The additional pulley allows them to only have to apply half the force.
After that, the two oldest boys offered to each do the pulling on a pulley, and everyone got to grab on the bar and get lifted off the ground. Yes, this is dangerous. Moms were on both ends. Children were never lifted extremely high off the ground and we always told them to be very gentle with the lifting and descending. It also helps to start with your arms already raised above your head to prevent should injury.
*No trees available?* The second time we did this lesson, we did not have a tree that we could use. Instead, we attached the pulleys to the top bar of a swing set using S hooks. We were not able to lift children as high, but it was still a fun learning experience!
YOU WILL NEED: 3 single eye pulleys or 2 single eye pulleys and 1 double eye pulley (We purchased pulleys at Lowes for $3 each.), 100 feet of rope (you'll be cutting it), 4 wooden handles (branches), and 2 wood screws with hooks (purchased at Lowes for about $2 each)
Song, Review, & Rube Goldberg Machines
12. Sing The Simple Machines Song
When it's moved by force we call it work,
but here's what I've been told:
Use any simple machine to help and ease that heavy load.
Wheel and axle, pulley, wedge
Screw, inclined plane, lever
When you learn to use simple machines
You'll show you are so clever.
The inclined plane is like a ramp,
a ladder, stairs, or hill.
Increase the distance = reduce the work.
Mechanical Advantage thrill.
The wedge is used to separate,
lift, or hold in place.
You use a wedge to cut your cakes,
Long and narrow = less force it takes.
Our levers come three different ways,
depending on the fulcrum.
Lift, squeeze, cut, pull, haul, or toss
to get all of that work done.
The screw just turns to do its job
- like opening your juice.
Or use the screw to hold things tight,
so that they won't get loose.
The wheel and axle turns around
to help you get things going:
Uphill, downhill, straight ahead,
your force or distance growing.
The pulley uses cord or ropes
or even chains or strings.
Pull longer distance with less force
To lift enormous things.
13. Five Minute Review of what we have learned about gears and pulleys.
14. Quickly discuss Rube Goldberg. Have children work in groups of 3 to create a Rube Goldberg - type machine to squirt toothpaste onto a toothbrush without anyone touching the toothpaste or toothbrush. (This is where the ball rolls down the ramp, which knocks into dominoes, which hit a cup that spills marbles that flow down a spiral, which fill up a cup, etc.)
-See who can do it in the most steps. See who can incorporate the most simple machines and even electricity into their contraption.
- Work backwards. Start by deciding what will be heavy enough to squirt the toothpaste out.
- If possible, assign each group a separate room so that they will have plenty of space. Allow children to use whatever they find in that room.
- Let children each grab a space and work on a separate part of the contraption. For example, let one child work on lining up dominoes, while another child devises a pulley system using a thread spool, some yarn, and a box. After everyone has completed a section, they can then work together to figure out how to connect each section.
- If one group finishes early, encourage them to continue adding sections to the beginning on their contraption.
- Assign a teacher/parent to each group to help guide the children and to make sure all the children are included in building it.
- After everyone has finished, let everyone watch each group's contraption. Be sure to video record this!
EVERYONE WILL NEED TO BRING ITEMS SUCH AS: a toothbrush, toothpaste, dominoes, tinker toys, marbles, shoe boxes, clothespins, dumbbells, disposable spoons, matchbox cars, ramps, funnels, balls, disposable cups, &/or whatever other toys/gadgets might be helpful
Simple Rube Goldberg Machine in Action
Simple Machines Lapbook Homework
If you'd like to create a Simple Machines lapbook this week, here are some options:
Optional Homework: More fun ways to learn about gears
My children love playing with these and seeing how far out they can get by connecting gears together and making them move other gears. The set is fairly durable and small, toddler hands can easily hold and place the chunky pieces. I also especially love that this comes with a handled storage container!
My family loves K'NEX sets and learn so much from them! This set allows your children to create 6 functioning gear models (such as a ferris wheel) and then your children can continue to build and create more designs with this fun set!
Looking for More Great Books?
Our Favorite Children's Books on Pulleys and Simple Machines in General
Pulleys to the Rescue (Simple Machines to the Rescue) by Sharon Thales was my children's favorite book on pulleys of the books that had photographs. Fred Flintstone's Adventures with Pulleys (Flintstones Explain Simple Machines) by Mark Weakland has cute illustrations and nice text to explain the physics behind pulleys. Levers and Pulleys: Lift Anything! (Iscience Readers, Level C) by Emily Sohn had great additional information on pulleys, but my 5 year old lost interest because there were too many words on each page for him. It was helpful for my 8 year old. How Do You Lift a Lion? by Robert E. Wells was my children's favorite book on simple machines. It shows how levers can be used to lift lions, wheels can be used to move pandas, and pulleys can be used to lift bananas to a tree-top monkey birthday party. It also includes vocabulary. We also really enjoyed the picture books Simple Machines (Let's-Read-and-Find-Out Science 2) by D. J. Ward, Simple Machines: Wheels, Levers, and Pulleys by David A Adler, and Smash!: Wile E. Coyote Experiments with Simple Machines (Wile E. Coyote, Physical Science Genius) by Mark Weakland, all of which cover multiple simple machines.
Great Video on Gears: The Way Things Work: Fun at the Fair
Fun Cartoon on Pulleys
Our Favorite Rube Goldberg Video
Good Video on Wheels & Gears
Ready for the next lesson?
Race cars down ramps as you study inclined planes and wedges, build and test catapults as you study levers and screws, create waterwheels as you study wheels and axles, lift each other using pulleys as you study gears and pulleys, use static electricity lift hair and separate salt and pepper as you study electricity, devise Rube Goldberg machines to place toothpaste on a toothbrush without touching either one, present on famous inventors, and more during this exciting 5 part hands-on unit study on simple machines and inventions!
- Inclined Planes and Wedges Lesson - This is part 1 of a 5 part hands-on unit on Simple Machines and Inventions. Race cars down ramps, compare carrying luggage to pulling it up an inclined plane, slice through apples using wedges, and more!
- Lever and Screw Simple Machines Lesson - This is part 2 of a 5 part hands-on unit on inventions and simple machines. Build and test catapults, lift an adult using a lever, test out screws of various threads, and more!
- Wheels and Axles Lesson - This is part 3 of a 5 part hands-on unit on Inventions and Simple Machines. Build and test waterwheels, use cylinders to make wheel cookies, experiment with matchbox cars to demonstrate friction, compare the mechanical advantage of an adult and a child's bicycle, and more!
- Gears and Pulleys Simple Machines Lesson - This is part 4 of a 5 part hands-on unit on inventions and simple machines. Build and test pulleys, play pulley tug-of-war, find out how a clock works, and more!
- Electricity Lesson - This is part 5 of a 5 part hands-on unit on inventions and simple machines. Watch static electricity lift hair and separate salt and pepper, build and test circuits and switches using household materials, play an electron game to demonstrate how electricity is conducted.
- Inventions and Simple Machines Presentations and Field Trip Ideas - Included are the presentations on famous inventors our students created following our 5 part hands-on unit on Inventions and Simple Machines. They also sang the Simple Machines song and ate a simple machine-themed lunch. (Recipes are provided.) Also included are the field trips we attended during this unit.
Would you like to teach this way every day?
Many of the activities from this lesson came from the Konos Volume 3 curriculum. I use Konos Curriculum as a springboard from which to plan my lessons. It's a wonderful curriculum and was created by moms with active boys!
If you're new to homeschooling or in need of some fresh guidance, I highly recommend Konos' HomeSchoolMentor.com program! Watch videos on-line of what to do each day and how to teach it in this great hands-on format!
© 2011 Shannon