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: Frictional force, normal force and coefficient of friction

  1. Apr 1, 2012 #1
    1. The problem statement, all variables and given/known data

    Calculate the frictional force, normal force and coefficient of friction for an 0.2kg object that is lying on a 35 degree incline.

    2. Relevant equations

    Ff= u x Fn
    F= m x a

    3. The attempt at a solution

    I managed to get FN= m x a x cos# = -9.81 x 0.2 x cos35 = 1.61 N

    I have no idea how to get Ff, but when I work that out I will be able to work out coefficient (u). Thanks for any help
  2. jcsd
  3. Apr 1, 2012 #2


    User Avatar

    Since the block is not accelerating, the net force must be zero. Look at all the forces, and find their components along the incline and normal to it.
  4. Apr 1, 2012 #3
    sorry also should have mentioned that 35 degrees is the angle the object starts to move down the slope
  5. Apr 1, 2012 #4


    User Avatar

    Staff: Mentor

    Hi lisa1991! http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    At 35° the component of gravity overcomes friction, so the forces are equal and opposite. Draw a diagram showing the incline and the direction of the forces involved.
    Last edited by a moderator: May 5, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook