Why a low gear climbs hills: gear ratios trade speed for force
30seconds
Pedal up a steep hill in the same gear you use on the flat and the pedals feel like concrete. Click to an easy gear and the climb gets bearable, but your feet spin and the bike barely creeps. Only a pair of toothed wheels changed.
Two meshing gears hand over the same number of teeth, so the ratio of their tooth counts sets both speed and force. Turning slower always means twisting harder. Drag the gears, change the teeth and watch speed and force trade places while their product stays put.
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