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: Finding the pushing force needed to keep object from sliding down wall

  1. Oct 15, 2011 #1
    This problem has been bugging me, seeing that my answer seems off. But who knows. Given the following measurements, find the required pushing force needed to keep a book from sliding down the wall.

    1. The problem statement, all variables and given/known data
    M= 2.88kg
    Coefficient of static friction= .322

    2. Relevant equations
    Seeing that the book can't move, I figured that F=Normal force
    mg=2.88kg(9.80 m/s^2)=28.2N
    force of static friction=μsN

    meaning F=N (Makes sense)

    meaning mg=μs(N)
    thus, N=(mg/μs)

    3. The attempt at a solution
    I did a simple substitution by setting F=(mg/μs)=(28.2N/.322)=87.6N

    To me, that answer seems a little high. So, is my reasoning and/or answer correct?
  2. jcsd
  3. Oct 15, 2011 #2
    The answer must be greater in magnitude than the weight of the book because friction coefficient < 1. Your answer looks good to me.
  4. Oct 15, 2011 #3
    That's good to know. Thanks.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook