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!

Frictional force

  1. May 5, 2006 #1
    An 18.8kg box is released on a 38.0o incline and accelerates down the incline at 0.281m/s2. What is the magnitude of the friction force impeding its motion.

    F = m*g*cos(38)
    sum forces parallel to the plane
    m*g*sin(38) - (mu)*(F) = m*a, or
    m*g*sin(38) - (mu)*m*g*cos(38) = m*a
    masses cancel out
    [9.81*sin(38)-(.281)]/[9.81*cos(38)] = .75 = mu

    but it says i'm wrong. i cant be.

    i only have one try left, and that's it.
  2. jcsd
  3. May 5, 2006 #2

    Doc Al

    User Avatar

    Staff: Mentor

    All you are asked to find is the friction force. No need to compute the normal force (what you call F, for some reason) or find mu. Rewrite your equation for forces parallel to the plane using "F" to represent the friction force.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Frictional force
  1. Frictional Forces (Replies: 1)

  2. Friction and forces? (Replies: 6)

  3. Force and Friction (Replies: 4)