Earth & climate · the experiment
Make the soda straw ring
Every soda straw in Choranche has its own notes, set by its length. Adjust the length to tune it to the blast, then to an earthquake, and see when it starts to resonate.
1 · The test blast
Beginner
According to the article, which straws did the 0.2 kg test blast threaten most?
Blast A shakes the cave wall. Adjust the straw's length so that its fundamental note, f₀, falls at the top of the blast spectrum.
2 · Twice as long
Intermediate
According to the article's beam formula, a straw's note varies as 1/L², where L is its length. A 15 cm straw rings near 175 Hz. Near what frequency does a 30 cm straw ring?
Lengthen the straw until its second note, f₁, falls in turn at the top of the blast spectrum.
3 · The earthquake
Expert
An earthquake shakes the cave slowly, between about 0.1 and 10 Hz. Using the same 1/L² law, which straws have their fundamental note inside that band?
The earthquake replaces the blast. Find the length of the straw measured by laser in the cave, from its fundamental note.
4 · The static method
Expert
A common method judges a stalactite from the rock's peak acceleration alone, as if it were rigid. For a 15 cm straw under blast A, what does it do to the stress?
Straw tuned
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