1. Not finding help here? Sign up for a free 30min 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!

Friction help

  1. Nov 13, 2006 #1
    stupid question because I forgot the equation

    What is the equation for the minimum value of the coefficient of friction?

    is it m(v^2/r) or v^2/gr
     
  2. jcsd
  3. Nov 13, 2006 #2
    check your units on them -- think about the units of the coefficient of friction -- then does one or the other make sense?
     
  4. Nov 13, 2006 #3
    the correct equation is v^2/gr right?
     
  5. Nov 13, 2006 #4
    well -- what are the units of that, and what are the units of the coefficient of friction?
     
  6. Nov 13, 2006 #5
    I know that the coefficient of friction is Newtons
     
  7. Nov 13, 2006 #6
  8. Nov 13, 2006 #7

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    It's what we "know" that hurts! The Newton is a unit of force. While friction is a force, the coefficient of friction is not.
     
  9. Nov 13, 2006 #8
    This then means that the first equation would have to be the right one based off of the units. And if Im incorrect than I guess I just forgot it all
     
  10. Nov 13, 2006 #9
    The units of the first are mass x velocity^2/length -- kg/m^2/s^2/m -- is that the same as the units of the coefficient of friction?

    Then analyze the second in the same way.

    Analyzing units always helps -- but of course doesn't guarantee the right answer.
     
  11. Nov 13, 2006 #10
    maybe I'm not understanding the units of the coefficient of friction. Could you explain to me what they are?
     
  12. Nov 13, 2006 #11

    OlderDan

    User Avatar
    Science Advisor
    Homework Helper

    The coefficient of friction is the ratio of two forces, the force of friction divided by the normal force. It has no units; it is a pure number.

    As for your original question
    This does not mean much out of context. By minimum value of the coefficient of friction I assume you mean the minimum value required to achieve some condition, such as the minimum value required to keep a block from sliding down an inclined plane or to keep a car going around a curve from skidding. There is no single equation for this. It comes from figuring out how much frictional force is required to acomplish something and dividing that required force by the normal force in the problem.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Friction help
  1. Friction help (Replies: 2)

  2. Friction help? (Replies: 1)

  3. Help with friction (Replies: 8)

  4. Friction help (Replies: 15)

  5. Friction Help (Replies: 7)

Loading...