1. Not finding help here? Sign up for a free 30min 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!

A Question about Frictional Forces

  1. Sep 21, 2009 #1
    1. The problem statement, all variables and given/known data
    A horizontal force of 15 N pushes a .50 kg book against a vertical wall. The book is initially at rest. If the coefficient of static friction= 0.6 and the coefficient of kinetic friction = 0.40, what is the acceleration of the book?


    2. Relevant equations

    F=ma
    static friction= coefficient of static friction x normal force
    kinetic friction= coefficient of kinetic friction x normal force


    3. The attempt at a solution

    First, I drew a free body diagram of a rectangle next to the wall. To the right, I had the force 15 N pointing towards the rectangle (the force exerted on the book). To the left, I had a force - 15 pointing towards the rectangle (the force exerted on the book by the wall). Pointing in the down direction, I had a vector mg. In the upward the direction the force is equal to the frictional force.

    Thus, the force in the x direction equals 0.

    Ff-MG= MAy
    Thus, Ay= (Ff-MG)/M

    Ff= coefficient of kinetic friction * normal force

    For some reason, I'm not getting a good answer. Can someone tell me where I am going wrong? Thanks!
     
  2. jcsd
  3. Sep 21, 2009 #2

    PhanthomJay

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    The maximum static friction force at the point of pending motion is (coef. friction)*N. The actual static friction force may be different. Does the block move?
     
  4. Sep 21, 2009 #3
    No it is not! I get it now! Thank you thank you thank you!
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: A Question about Frictional Forces
Loading...