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: How to find the coefficient of static friction.

  1. Oct 23, 2012 #1
    1. The problem statement, all variables and given/known data
    In order to hold a book of mass m stationary against a wall, you must push horizontally with a force of at least P.
    a. make a force diagram and find the coefficient of static friction
    b. calculate the coefficient of static friction for the wall and book when at least a 35-N horizontal push is needed to hold a 1.2-kg book steadily at rest against the wall.

    2. Relevant equations
    3. The attempt at a solution
    I find it difficult to grasp the concept that, somehow, there is still friction between the wall and the book even though there is no velocity. My best guess would be:

    F_f = F_net so μ would have to equal 1. help would be greatly appreciated.
  2. jcsd
  3. Oct 23, 2012 #2
    If there is no velocity and no acceleration, the system is in equilibrium. Try drawing the force diagram without the static friction and then you'll see how friction plays a role.
  4. Oct 23, 2012 #3
    so is friction equal to weight?
  5. Oct 23, 2012 #4
    Yes, and knowing that and the basic equation of static friction (f=μ*n), you can now calculate μ.
  6. Oct 23, 2012 #5
    great, I see. thank you so much.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook