Wednesday, July 22, 2009

30 Second Science - Toilet Paper Tube Columns

I got the idea for this activity from the PBS Building Big website. They also have some very clear instructions for making a geodesic dome out of newspaper, similar to what we did a couple of posts back. The idea behind this little activity is to demonstrate the importance of compression for strengthening load bearing columns.

We used:

  • 4 toilet paper tubes, sealed on one end with masking tape (we wrapped masking tape all the way around one of the tubes too)

  • enough popcorn kernels to fill one of the tubes

  • sand (we actually ran down to the local park, so we could some of the sand from around the play equipment).

Using a picnic table for balance, I had my oldest son try to put his weight onto one of the empty toilet paper tubes. Of course, it crumbled almost immediately.

Next, we filled one of the tubes with popcorn kernels, before he stepped onto it. This column lasted a little longer, but started to crumble as well. We had some difficulty though, telling whether it crumbled simply because of his weight, or if it was because he put a little more weight on one side of it, than the other. It's important to place your foot evenly over the top of the tube.

Then, we filled a tube with sand. This time it held his weight without any problems. In fact, it held my weight without any problems (I won't tell you how much weight that was, but it was more than his). Finally, we mixed sand, and popcorn kernels together in the tube. This column held the weight as well.

The idea, is to demonstrate how the sand, or popcorn kernels, distribute the weight evenly, as they are compressed into the tube. This strengthens the weak outer material, and allows it to bear up under much greater pressure, than it could handle if it were empty. The outside wall, only has to be strong enough to hold the compressed material in.

This was a pretty good activity for the entire family. The older kids got a dose of science, while the younger ones got a chance to play at the park. And, it was quick enough, that we were there and back before anyone needed sunscreen.

It's great to be a homeschooler.

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