Activities Index | Handout | Educator Ideas
(per group of two)
2 empty toilet-paper tubes (but have lots of extras, as kids will want to try again and again)
sand or salt
dishpan, tray, or
cardboard box lid to catch any spilled sand or salt
After the activity, show "Chicago" from Skyscrapers
to demonstrate how columns support loads in compression. (Check the Program Description to locate this show segment.)
Try the Forces Lab.
For more information, see Additional Resources.
Hold up a toilet-paper tube and announce that you are going to stand on it. Ask: Do you think this tube will hold me up? (Kids will probably say no; if they say yes, ask what the maximum weight they think it can support isa car? an elephant?). Now introduce the activity challengeto find a way to make a toilet-paper tube support a person's weight.
Lead the Activity
Supervise this activity carefully to ensure kids' safety. Limit testing to one person at a time. Have someone sit in the chair to hold it steady while the tester leans on the back of the chair.
Instruct kids to step evenly on the top of the tube. They may observe on their own that a slight lean in any direction causes the tube to crumple more quickly on that side. Placing a piece of cardboard over the top of the tube may help distribute weight more evenly.
The Big Idea
Kids may find different solutions to increase the strength of the tube. Reinforcing the sides of the tube by wrapping it with bands of tape makes it a little stronger. The tape increases the stiffness of the sides of the tube and helps it resist buckling under the load.
Placing tape over the ends of the tube and filling the tube with sand or salt increases its strength enough to hold a person's weight. The load is distributed evenly by the material inside the tube. The sand's tendency to spread out is resisted by the sides of the tube, which hold it in and enable it to support the load. In construction, a thin-walled column can be filled with inexpensive material which still greatly increases the column's strength in compression.
Build on It
Supply additional materials (such as marbles or pebbles) for kids to test their predictions. Possible outcome: Kids may find that the smaller particles work better because they push out more evenly against the sides of the column.
Math Use the tubes to discuss circumference, diameter, and area of circles. Ask kids to predict which can support a greater weight: a single column with a circumference of 24 cm or three columns with circumferences of 8 cm each? Have them test their predictions.
Possible outcome: Kids will probably find that the answer depends on how they arrange the columns. Three smaller columns arranged a small distance apart in a triangular shape may support more weight than a single large central column.