You won't believe how many science projects you "can" do with a couple of tin cans.
Before we start the physics, however, let's do a bit of chemistry. Is what we call a "tin can" really made of tin? How would you check?
It seems that the can our beans come in should be called a steel can because it is made mostly of steel, although it may have a light coating of tin to prevent rusting. Technically, if a can were made only of tin a magnet should not stick to it. Magnets are attracted to cans that contain iron, usually in the form of steel. Is a magnet attracted to your can of beans? What about an aluminum soda can? Pick up a magnet and find out.
What got us started with tin cans this week was an article in a book that promised you could get a tin can to roll uphill. When it did not work as the book suggested it should, we decided to investigate further.
Activity 1. Uphill Rolling Can
- Clean, empty tin can* or similarly-shaped plastic container
- modeling clay
- cookie sheet or similar flat surface and a couple of books to make an adjustable ramp
- rubber bands (optional) to give the can more grip
* Remove the lid of the can with adult supervision, and make sure there are no sharp edges.
Roll the can across the floor or on a table to see how it behaves. Build a ramp with a slight incline with the books. Try to roll the empty can up the ramp. What happens?
Now roll out a lump of the clay into a worm or snake shape. Attach the clay to one side of the can on the inside (see photograph). Roll the can across the floor or table. Does it behave differently than it did without the clay?
Try the ramp. Start the can with the clay up versus the clay down, until you can get the can to roll uphill. If it doesn't work for you, adjust the steepness of the ramp. You can also put rubber bands around the outside of the can to increase grip. Make sure they are even so they don't over balance the can.
Activity 2. Tin Can Car
You can take the idea of a self-propelled tin can a step further by creating a rubber band-driven version.
The idea is to put two holes in each end of the can (or can lids) that line up with each other, slip a rubber band (or similar elastic material) through the top holes and then add a weight in the center, in the middle of the can. Slip rubber bands through the bottom holes. Tie the ends. Roll the can and it should roll back on its own from the weight in the center.
PBS Kids has a good description of how to make a can car.
Description of a similar device from the November 1910 issue of Popular Mechanics. Be aware that ideas of safety were different back then. For example if you try this one, you should use a zinc sinker (available at fishing supply stores) rather than lead.
Activity 3. Tin Can Telephone
A classic activity is to make a telephone using two tin cans and a piece of string.
- two clean, empty cans with the tops removed (or plastic cups work, too)
- goggles (for eye protection while hammering nail into can)*
- string at least a few feet long
*Unlike in the video below, children should perhaps wear eye protection while creating the hole in the bottom of the can.
Hammer the nail into the center of the bottom of each can to create a hole. Remove the nail. Feed the string through the holes and tie a knot so that the knot prevents the string from coming out through the bottom. Both cans should now be connected by the string. Hold the two cans far enough apart so the string is tight. Take turns talking into the can and then listening to the other person talk.
You can even decorate your can like they did in this short video.
Activity 4. Musical instruments
- clean, empty can or cans of various sizes with the tops removed
- large balloons, at least one per can
- chopsticks (optional)
Cut the stem off of a balloon and roll it over the top of a can. This is not as easy as it sounds, but if you can get a tight fit you will have a wonderful drum. Use hands or chopsticks to drum on the balloon top. Compare sounds of different-sized cans.
Activity 5. Sand Resistance (Advanced)
- two cans
- play sand
- bin large enough to accommodate the two cans standing up plus sand
Fill a large bin with play sand. Press one can into the sand with the open end down. Press the other into the sand closed end down. Which has the most resistance? Sounds simple, but there are some complex physics involved.
To see the expected results, watch this video
For an explanation of the open can versus closed can in bucket of sand, see Science Now (website does contain ads).
A Few Other ideas:
Information about a stirling tin can engine in the Doable Renewables book review
When you are done with your can, remember:
"...one plant in a tin-can may be a more helpful and inspiring garden to some than a whole acre of lawn and flowers to another.” ~ Liberty Hyde Bailey
Hope you have fun with your tin cans.
Let us know how the activities turn out and if you have any other ideas for science with tin cans.