How exactly do the different gears on a bike change how easy it is to pedal? And why is it that despite being at the appropriate gear, it is still harder to climb uphill despite the same pedals per minute?

Question

How exactly do the different gears on a bike change how easy it is to pedal? And why is it that despite being at the appropriate gear, it is still harder to climb uphill despite the same pedals per minute?

In: Physics

Answer 1

Imagine a gear with 5 teeth. It takes 1 full rotation to turn a gear with 5 teeth. Now replace that second gear with one that has my teeth. It takes 2 full rotations of that gear to make that same distance turn. Flip it around so that the 10 tooth gear is turning the 5 tooth gear. Now it only takes half a turn of the first gear to spin the second all the way around. Smaller gears turn more quickly, but generate less force. Larger gears turns slowly but generate less force.

When we go up a hill, we are working against gravity which wants to pull us back down that hill. It takes more energy to do that whether we are using the gears to make many quick rotations, or one slow rotation.