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: Static Friction Ladder Problem

  1. Nov 11, 2011 #1
    1. The problem statement, all variables and given/known data
    See attachment.

    2. Relevant equations
    F = μN

    3. The attempt at a solution
    I attached the FBD I drew. I then did
    ƩFx = FA + FBcosθ - NBsinθ = 0
    ƩFy = NA -W + NBcosθ + FBsinθ = 0
    ƩMA = 19.5NB - 3.75W = 0
    ƩMB = 3.75W - 7.5NA + 18FA = 0
    FA = μNA
    FB = μNB
    θ = arctan(18/7.5) = 67.38°

    I know μ is supposed to equal .18, but I can't get it. I've tried substituting different things I don't know how many times now, and I can usually get to an expression of just μ or μ and θ, but I can never get it to equal .18.

    Attached Files:

    Last edited: Nov 11, 2011
  2. jcsd
  3. Nov 11, 2011 #2


    User Avatar
    Homework Helper

    The angles at the wall are wrong on your FBD. They should both be 90-theta.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook