1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How does gear system amplify force?

  1. Jun 20, 2013 #1
    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. jcsd
  3. Jun 20, 2013 #2


    User Avatar
    2017 Award

    Staff: Mentor

  4. Jun 20, 2013 #3
    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"?
  5. Jun 20, 2013 #4


    User Avatar
    Homework Helper

    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.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook