An updated version of this post can be found here.
During our Simple Machines unit, the last simple machine we studied was Wheels and Axles.
Key concepts of wheels and axles:
When you try to push a load across the ground, there’s a lot of friction that makes it hard to move. The whole surface area of the load is on the ground. When you put the load on wheels, then there’s only friction on the very small part of the wheel that is touching the ground at any given time. Thus, it’s much easier to move a heavy load over a long distance.
First, have the kids push a heavy load across the floor. Then give them round dowels, and have them put the load on top of a row of dowels and push it… the dowels act as “wheels” and make it much easier to move the load (you can note that we think ancient Egyptians may have rolled large stones on logs while making the pyramids). However, they soon discover that as you do this, the load rolls off of the dowels, and you have to move the dowel back to the front of the row over and over. There’s a great description of someone doing this demonstration with their child here. But I would do two things differently than the post: Work on a carpeted floor, so there’s lots of friction. Use a basket instead of a smooth cardboard box – again, this increases the friction so better illustrates the benefit of the dowels.
There’s also a nice post here on using a brick and pencils to illustrate this concept.
Next, you could teach the idea of wheels and axles, and mounting the load on a set of wheels and axles. There’s lots of ways you could do this… but I like this one: put a grown-up on a board. Put the board on two scooters or skateboards and push the grown-up around. http://www.littleblastblog.com/2014/09/wheels-make-it-easier-to-push-daddy.html
Free play: We got these great wheels that can be attached to any cardboard box. They’re really well built and easy for a small child to use. And any time you’re done with a box creation, you can take off the wheels and save them for the next time. We had one box with wheels, and one box that was the same size without wheels. Kids could load them up and see which one was easier to move.
We also had wooden dowels, and a basket – kids could load up the basket and roll it back and forth on the dowels.
Building: LOTS of building toys include ways to make wheels and axles: Duplos/Legos, Tinkertoys, K’NEX, and so on. Put these out for free play.
Observation: Encourage children to find all the wheels they can in and about the classroom (toy cars and trains, trikes, bikes, door knobs, and so on.) Encourage them to notice how the wheels work. One thing to notice is that with some things, the axle is fixed to the wheels and rotates with the wheels. But, in other cases, the axle is stationary and the wheels rotate around it (e.g. a skateboard).
Exploration: This post focuses on showing the difference between how balls roll and how wheels roll by making a set up wheels and axle from a Styrofoam ball: http://www.littleblastblog.com/2014/09/wheels-center-of-ball.html
Build a car: There are many ways to build toy cars from recyclables. This one uses buttons, a clothespin, and a straw: http://almostunschoolers.blogspot.com/2010/12/clothespin-button-racer.html. This uses toilet paper tubes, wooden skewers and either paper or rubber wheels: http://nerdybaby.blogspot.com/2012/01/sail-cars-preschool-preview.html
This one uses a paper towel holder for the car body, CDs and cardboard disks for wheels, and pencils for axles, and makes it a movable car by adding rubber bands: http://makeitatyourlibrary.org/play/easy-rubberband-car#.VignPDZdGM-
Product-based art: We made game spinners. We punched a hole through the center of paper plates, and a hole in the center of popsicle sticks. Kids decorated the plates however they wanted to. We took a brad (paper fastener), threaded it through the stick, then a washer, then the plate. We spread out the arms of the brad on the other side of the plate, and taped them in place. Poof – it’s a spinner.
We made tops with dowels and wooden circles. If you don’t have wooden disks, you could use cardboard. Kids could decorate if they chose, and then play with for as long as they wanted to.
We made pinwheels. We cut paper squares into pinwheel shapes, threaded a brad through a hole, then through a short length of straw, then into the straw handle. I have to confess that these weren’t successful… It was hard for the kids to cut the paper just right – it might work out OK if all your students were 5 and up, but not for our younger kids. Also, the connection was too tight, and they just didn’t turn well. A longer brad might have helped with that. The end product looked great, but wasn’t as dynamic as we hoped.
Water table and sensory table: We have water wheels they were able to play with. It would be really cool to build your own water wheels. Here’s ideas on how to do it: http://iijuan12.hubpages.com/hub/wheels-and-axles-lesson-plan-in-simple-machines-unit
Song: The Wheels on the Bus, of course! Another option is Bumping Up and Down in My Little Red Wagon, which includes the words “One wheel’s off and the axle’s broken.”
Outdoor time: Bikes, Trikes, and Wagons, oh my!
For a wheels theme, you could obviously do LOTS of activities related to cars. We did a whole week just focused on cars as a complex machine.
There’s lots of other great ideas for wheels and axles activities here: http://iijuan12.hubpages.com/hub/wheels-and-axles-lesson-plan-in-simple-machines-unit
Addendum: next year, we’ll add in a building project, making this cool Duplo top launcher.