Physics
2 breaks
Forces, light, time and the odd behaviour of the very small.
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Why a siren drops in pitch as it passes: the Doppler effect
An ambulance siren sounds high as it comes at you and drops the moment it passes, yet the driver hears one steady note. The trick is in how crests per second…
Why a boat's wake is always a 39° V: Kelvin's wedge
Behind every boat spreads a V of ripples, and it is always about 39° wide, whether the boat crawls or speeds. Lord Kelvin worked out why in 1887: only waves…