# How does gear system amplify force?

1. Jun 20, 2013

### null void

If i have a small spur gear, and i rotate it and transfer the rotation to another gear with bigger pitch diameter. The output gear(bigger gear) will turn slower right? then does this mean the torque force transferred to the output is greater?

So when the output gear is connected to a rope to pull something up, i have to convert the torque force to by dividing the radius?

2. Jun 20, 2013

### Staff: Mentor

Right
Right

3. Jun 20, 2013

### null void

Here is the real question, if i have a input gear with radius r, and output radius of 2r, when i apply force, f on input gear, the output gear can produce torque force of 2rf ?

when converting the torque force into force, i get f back as the output?

Does this mean the gear can't amplify "force"but they can amplify "torque force"?

4. Jun 20, 2013

### rcgldr

If you're applying the force on the outside of the first gear, and the second gear is applying a force from it's outside, then the force is not increased. Imagine a chain wrapped partically around the two gears and that you're pulling on the chain. The chain's speed is the same everywhere. In order to get a leverage like effect where the force is increased, then the "output" speed needs to be slower than the "input" speed. There are various ways to do this.

A gear system is normally used to increase torque and decrease angular velocity. or to decrease torque and increase angular velocity.