a bus with wheels of radius 2 meters (it’s a monster truck bus). I’ll say how fast the wheels are turning and you say how fast the bus is moving. Ready? “The wheels are turning 2000 degrees per second”. You’d think: Ok, the wheels are going 2000 degrees per second. That means it’s turning 2000/360 or 5 and 5/9ths rotations per second. Circumference = 2πr, so it’s moving, um, 2 times 3.14 times 5 and 5/9ths... where’s my calculator... “The wheels are turning 6 radians per second”. You’d think: Radians are distance along a unit circle — we just scale by the real radius to see how far we’ve gone.
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