How can you tell a good idea from a bad one? You can get some data or do some calculations. I have been having fun reading xkcd web cartoonist Randall Munroe’s latest book, How To: absurd scientific advice for common real-world problems. There are 28 chapters beginning with How to Jump Really High and ending with How to Dispose of This Book. For the first one he says you can either devote your life to athletic training or cheat, and the pole vault is a good way to cheat. Randall shows an equation for how high you can get, which comes from the simple energy transfer consideration I have shown above in an image.
Chapter 2 is on How to Throw a Pool Party. For an above
ground pool (a circle with a 30 foot diameter) Randall uses the Barlow formula
for stress from the weight of water to calculate how deep you can make a
pool using aluminum foil (just five inches) or an inch of wood (75 feet).
If you think a border wall is beautiful, then you probably
would like Chapter 9, How to Build a Lava Moat (around your home). But, as is discussed
in the four-minute YouTube video shown above, this turns out to be a very bad
idea.
My favorite is Chapter 5: How to Make an Emergency Landing (A
Q & A with test pilot and astronaut Chris Hadfield). Chris discusses a lot
of different situations, including how to find a place to land the space
shuttle. Runways for the shuttle are 15,000 feet long (nearly three miles).
They carried a book showing every possible emergency runway in the world and the direction you could land - which Randall
illustrated via a cartoon of a book cover titled BABY’S FIRST emergency
spacecraft landing.
There also are full-page cartoons discussing How to Listen
to Music, Chase a Tornado, Go Places, Blow Out Birthday Candles, Walk a Dog,
Build a Highway, and Change a Lightbulb.
The pole vault image came from Pearson Scott Foresman at
Wikimedia Commons.
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