Have you ever played with one of those toy cars that you push backwards and then it zooms forward on its own?
We had so much building our own version with this rubber band car STEM activity.
This activity uses recyclables and materials that are easy to find. It is sure to become one of your favorite STEM activities for kids.
This rubber band STEM is perfect for learning about potential energy.
Rubber Band Car STEM Activity
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- Empty Paper Towel Tube
- 4 Unwanted CDs
- Two 6-Inch Craft Dowel Rods (or a wood skewer cut in half)
- Hole Puncher
- Paper Clip
- Variety of Rubber Bands
- Masking Tape
- Colorful Duct Tape, Markers, Stickers (optional)
You can find this project and over 50 more fun engineering activities in my new book, Awesome Engineering Activities for Kids.
How to Make a Rubber Band Car
Start by using your ruler and pencil to draw a straight line from one end of the paper towel tube to the opposite end. This will help make your wheels straight and parallel with each other.
Slide your hole puncher through one end of the paper towel tube as far as it will go and punch a hole on the line you drew. Then do this on the opposite side of the cardboard tube.
Use your ruler and pencil to draw another straight line on the opposite side of your tube and once again use the hole puncher to punch holes at each end of the tube.
Once the holes are made, slide your dowel rods through the holes.
Check and make sure the dowel rods are parallel with one another. Your car won’t work if one axle sticks up while the other is resting on the floor.
If necessary, you can rotate the tube and make new holes.
Decorate your race car using colorful duct tape, markers, or stickers. Just be sure you don’t cover up the holes the axles go through!
Once your decorating is finished, insert your dowel rods back through the holes.
You will be using old CDs as your rubber band car’s wheels. To keep the CDs from slipping off the dowel rod, wrap masking tape around both ends of the dowel rods about one inch from the ends. You will need 2-3 feet of tape for each one, depending on how tightly and smoothly you wrap the tape.
When you are finished push the CD over the tape. It should be snug. If it is wobbly, remove the CD and wrap a bit more tape around the dowel rod and try again.
Now it’s time to make your “engine.”
Make a chain with 5 rubber bands. Try to use all the same size rubber bands. (We used rubber bands that were approximately 2 inches long.)
Attach a paper clip to the end of the chain.
Carefully wrap the paper clip end of your rubber band chain around the back axle of your car, inside the cardboard tube. Thread the paper clip through the last rubber band of the chain and pull, making a loop to secure the chain around your axle.
You may need to add a piece of tape to help hold the rubber band tight against the axle.
Now drop the paper clip end back through the tube so the rubber band chain is hanging inside the tube.
If the chain hangs outside the cardboard tube more than an inch, you will need to remove one of the rubber bands and then reattach the paper clip.
Secure the paper clip to the cardboard tube, making sure no rubber bands are rubbing the front axle.
To wind the car’s engine, hold onto your back axle (the one the rubber band chain is connected to) and rotate the axle to wind the rubber bands around it. (If they don’t wind around the axle, try turning it the opposite way.) We used a similar method in our rubber band boat.
While still holding the axle, set your car on a flat surface.
Let go and watch it zoom forward!
This project may take some tinkering to make it work properly. That’s part of engineering: seeing what works and what doesn’t and then making necessary changes.
If your wheels are wobbly, the car won’t go as far. Try wrapping more tape around the axles to make the wheels steadier.
If the wheels turn but your car doesn’t move, there may not be enough friction between the wheels and the ground. Try the car on a different surface.
Extension Activities for this STEM Activity
- What happens if you change the size of the rubber bands you use? Try using thicker rubber bands. Or try using rubber bands that are shorter. Does the size of the rubber bands affect how the car operates?
- What happens if you take off a rubber band or if you add one to the chain?
- Try this project with a friend or family member and race your cars. Whose car goes the farthest? Can you figure out why?
Why the Rubber Band Car Works
When you twist the rubber band around the axle, you give it potential energy. The more you twist it, the more potential energy it has.
When you let go the rubber band goes back to its original position, and the potential energy is turned into kinetic energy, causing the back axle to spin. When the axle turns, the wheels attached to it also move, and the car goes forward.
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