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Secrets of Lost Empires II -- Roman Bath
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Classroom Activity
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Objective
To discover that you can build an arch that supports itself with no
mortar.
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copy of "Tasty Arch" student handout (HTML)
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10 sugar wafers (the flat kind with two cookie layers; use fresh
cookies; soft, stale cookies are difficult to sand)
- piece of 50 grit coarse sandpaper
- plastic knife
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Have students follow directions on the "Tasty Arch" student
handout.
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Provide students with this additional information:
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Try to keep the sanded edge of the cookie flat, not rounded.
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Do NOT sand both sides of the cookie; too much sanding
weakens the blocks.
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Replace any badly broken cookie blocks with new ones.
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When constructing the arch remember: Too many cookies make a
circle and too few will not complete the arch.
In an arch, the top stones distribute their weight to the blocks on
either side and will not fall unless they can push the stones
beneath them sideways. Stable arches, therefore, require that side
stones be firmly set in place. The riverbanks of Chinese rainbow
bridges provided this sideways support. The multiple arches in Roman
aqueducts and the double arches of the Roman baths had similar
support.
Arches are unstable during construction until the two sides meet in
the middle. To experience the instability, have students stand back
to back with a classmate with their shoulders touching. Have them
slowly step away from each other, but keep their shoulders in
contact. The two students maintain stability because the weight of
their bodies is distributed down and sideways through each other's
legs. If either were to move away suddenly, both would crash to the
floor.
Raising the arch requires some dexterity. Remind students to apply
inward pressure on the cookies to keep them in line. Tell them that
early engineers built scaffolding to hold the stones in place until
the arch achieved its own stability.
National Science Education Standards
Grades 5-8/9-12
Standard B: Physical Science—Motions and Forces
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