Archimedes and the Law of the Lever

"Give me a place to stand on, and I will move the earth."

quoted by Pappus of Alexandria in
Synagoge, Book VIII, c. AD 340

the 140 lb boy 2 feet from the fulcrum (center of gravity)
his 70 pound sister 4 feet from the fulcrum

2 x 140 = 4 x 70

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