Home School Life Journal From Preschool to High School

Home School Life Journal ........... Ceramics by Katie Bergenholtz
"Let us strive to make each moment beautiful."
Saint Francis DeSales

Building Lab, part 3: Columns and Arches


What role does the column take in architecture and building? Columns are often used to hold up heavy loads such as the roofs of buildings, which pushes on the column, putting it in compression. Therefore, a good column, then has to be very strong in compression.

Can a toilet paper tube then support your weight? 

Tell your students that you are going to have them place an empty dishpan, tray, or box lid on the floor, and then they are to stand an empty toilet-paper tube (the column) on one end in the pan. While holding on to the back of the chair with both hands, they will gradually press straight down on the top of the column with one foot. Have them predict whether a toilet-paper tube can withstand the compression caused by their weight. Have them explain the reason for their prediction.
Note: If your students are very young (and light) they may be able to stand on the toilet paper tube without collapsing it. This is because the tube is round and is able to distribute the compression all around evenly. If this happens to you, have an older, heavier student test it, and then you, the teacher could also test it. 
Once you do have a collapsed tube, have your students observe it to see where it failed. Have your students now brainstorm ways in which they could make the column stronger, using only tape and sand? Repeat standing on the column, using the second toilet-paper tube and your new design.

How did the strength of the two columns compare? Have your students think about why the results of the two were different. Next, tape the ends of the tube and fill it with sand. The tube now can distribute the compression of the weight outward from each sand grain and can now hold the weight, not only of your heaviest student but of an adult as well without collapsing. Wonder how much weight it would hold before it collapsed?

What can this experiment tell us about the best building materials?

For Older Students


Use the tubes to discuss circumference, diameter, and area of circles. Ask students 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. Students 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.


Arches



An arch is a curved structure that converts the downward compression force of its own weight, and of any weight pressing down on top of it, into a force along its curve. This results in an outward and downward force along the sides and base of the arch. 

A buttress is a side support that counteracts an outward pushing force, the way bookends keep books on a shelf from sliding sideways. Buttresses are often used to support the sides of arches and tall cathedral walls, where they counteract the outward thrust.

Have two students form an arch by placing their palms together and leaning toward each other, sliding their feet as far back as they can. Caution them not to lose their balance. Ask the students where they feel a push or a pull. Next have a third student gently pull down on the top of the arch to test its strength. They should find it not too difficult to break the arch.
Now guide them to the idea of adding buttresses by asking additional students to reinforce the legs and feet of the arch-makers. Ask the how stable their legs feel now. They should see a large difference in their ability to resist the pull at the top of the arch now.

1 comment:

  1. This may appear twice because I got a weird response, but I'm totally stealing this for next year for using with the Greeks.

    ReplyDelete

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