Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Which class of levers is the most 'efficient'?

  1. Jun 4, 2005 #1
    I am a dental student. I have noticed that dentists tend to say that Class III levers (eg. the human mandible) are "the least efficient type of lever." I told my friends that this was incorrect, because there is no more inherent energy loss in a Class III lever than I or II.

    The next day my colleague told me that Class III levers are the least efficient because, for a given input of Work, you get the least amount of Work back out. But I don't think this is right either. From what I remember from college physics, all three types of levers conserve Work. So you get out the same amount of Work that you put into the lever. The only things that are changed are the Force and Distance -- right?

    So am I right in thinking that Class I, II, and III levers are all equally efficient, whether you define efficiency in terms of Energy or Work? Or, if my colleagues are right, how are Class III levers the least efficient?

  2. jcsd
  3. Jun 4, 2005 #2

    Doc Al

    User Avatar

    Staff: Mentor

    mechanical dis-advantage

    You are correct. Your colleagues are confusing efficiency with mechanical advantage (the ratio of output force to input force). They are probably trying to say that Class III levers have the lowest mechanical advantage: For Class III levers the input force is larger than the output force.
    Last edited: Jun 4, 2005
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook