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

I can not assume the sense of the friction force?

  1. Aug 16, 2008 #1
    With all the mechanical forces in statics problems I can assume the sense and I might get a negative answer which implies I made the wrong assumption. But why can I not do this with the friction force when using the equation F=uN?
     
  2. jcsd
  3. Aug 16, 2008 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Because the direction of friction is not independent of other variables. For example, if you assume something slides to the right, then friction on it must point left.

    Perhaps discussing a specific example would help, if you have one.
     
  4. Aug 16, 2008 #3
    Besides, the equation you mention is not a vector equation, so you can't use it to find direction. It can't be a vector equation, because in ordinary cases the normal force and frictional force are perpendicular.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: I can not assume the sense of the friction force?
  1. Friction Force (Replies: 2)

  2. Force of Friction (Replies: 11)

Loading...