- #1

Jimmy87

- 686

- 17

## Homework Statement

I am really struggling to understand gears and how they can multiply force or speed. I was reading over this physics link (http://www.tutorvista.com/content/physics/physics-i/power-energy-machines/gears.php).

## Homework Equations

## The Attempt at a Solution

I'm confused about the whole "force x distance" idea. In this link it says cog A rotates twice for every turn of cog B so must be moving faster which I get. However it then talks about cog A moving twice the distance and so experiences half the force. My line of thinking is that the circumference is smaller on the smaller cog so although it is moving faster it is still covering the same distance as the larger cog in terms of circumference so then wouldn't the forces have to be the same? I thought the forces would be the same anyway because of Newton's 3rd law. Wouldn't a tooth of cog A exert a force on a tooth of cog B and cog B exert and equal and opposite force back on cog A?