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Homework Help: Help help

  1. Oct 25, 2006 #1
    Coefficient of kinetic friction

    :confused: so im working on the force of friction and overcoming friction
    i know that the coeffcient of friction is equal to the kinetic force over the normal force and i can get these when hte system is on a horisantal surface
    But i dont understand how to get them with an incline

    Problem: a box slides down a 30 degree ramp with an acceleration of 1.2 m/s squared. Determine the coefficient of kinetic friction between the box and the ramp.

    im not sure i even know where to start, well i have a free body diagram
    Last edited: Oct 25, 2006
  2. jcsd
  3. Oct 25, 2006 #2
    ok so i got that the force perpendicular (x) - (subtract) the force of friction = mass*acceleration of x
    but the question does not give you a mass!
    how do i determine the normal force if i don't have a mass?
  4. Oct 25, 2006 #3
    What is the acceleration down the ramp with no friction?

  5. Oct 25, 2006 #4
    um it says 1.2 m/s squared
  6. Oct 25, 2006 #5
    That is WITH friction. What is it without friction?
  7. Oct 25, 2006 #6
    how do i find that out? i dont know what the force of friction is in this problem
  8. Oct 26, 2006 #7
    Well, let me put it to you this way. You have a freebody diagram. What are your force equations? Let's take a look at those.
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