Gears are all around us.  Clocks, cars, bikes, even your printer has countless gears! For the purposes of this analysis, we'll focus on two properties of gears: gears can be used to multiply torque and used to change speeds.

Why is torque important here? Winding the spring in this toy requires significant torque.  But this is product for kids, so how can we make it easier for them? The answer is gears! Gears give the kids a mechanical advantage. Now the kids only need to input a modest force to wind up the stiff spring.