Physics
2 breaks
Forces, light, time and the odd behaviour of the very small.
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Why a skater spins faster when she pulls her arms in: angular momentum and r squared
A skater starts a slow spin with her arms wide, pulls them in, and blurs into a fast spin with no push from anything. The trick is a quantity that cannot…
Why a tossed tennis racket flips: the intermediate axis theorem
Spin a tennis racket about its handle or its face and it flies cleanly. Spin it about the third axis and it flips, even in orbit where nothing pushes on it…