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Old 05-20-2019, 01:01 PM   #14 (permalink)
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That's one of those things that people "know" intuitively: that coasting downhill makes up for expending energy to get up the hill in the first place. In a simplified, idealized world where cars have no aerodynamic drag, no rolling resistance, and no drivetrain inertia or friction, that would be true. But the world is a lot more complex than we imagine most of the time.

I'm working through White's Fluid Mechanics this summer, and the first chapter starts with a discussion of one deceptively simple question: What is the difference between a solid and a fluid? The author points out that most laypeople, even though they "know" what makes the two states different, can't actually define it.
UIUC Aerospace Engineering
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