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Secrets of Lost Empires II -- Roman Bath

Classroom Activity


Objective
To discover that you can build an arch that supports itself with no mortar.

Materials for each team
  • copy of "Tasty Arch" student handout (HTML)
  • 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
Procedure
  1. Have students follow directions on the "Tasty Arch" student handout.

  2. Provide students with this additional information:

    • Try to keep the sanded edge of the cookie flat, not rounded.

    • Do NOT sand both sides of the cookie; too much sanding weakens the blocks.

    • Replace any badly broken cookie blocks with new ones.

    • When constructing the arch remember: Too many cookies make a circle and too few will not complete the arch.

Activity Answer

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.

Standards

National Science Education Standards
Grades 5-8/9-12
Standard B: Physical Science—Motions and Forces

Teacher's Guide
Secrets of Lost Empires II -- Roman Bath
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