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!

Homework Help: What is the friction force?

  1. Dec 29, 2008 #1
    1.Quick question: a 12kg mass is on a 30 degree incline where the coefficient of static friction is 0.8. What is the friction force exerted on the mass?

    2. F = ma, f = uN

    3. I got around 83 N for this. All I did was multiply the coefficient of friction by normal force, which was Wcos30 in this case. So, 0.8 * 12 * 9.81 * cos30, giving me around 83 N, but my answer sheet says 60 N....
  2. jcsd
  3. Dec 29, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Remember, the static friction force is equal to uN only when the object is about to slide relative to the surface. Is it? What is the component of the gravity force acting on the object down the plane?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook