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Box of Mass Friction Problem

  1. Oct 6, 2013 #1
    1. The problem statement, all variables and given/known data

    A box with a mass of 2.2 kg sits on top of another box with a mass of 3.8 kg. The coefficient of friction between the two boxes is 0.25, and the coefficient or kinetic friction between the larger box and the horizontal surface is 0.32. Determine the largest horizontal force that can be applied to the larger box so that the smaller box does not slip off.

    2. Relevant equations

    Let fs be friction static
    Let fs be friction kinetic

    Fnet = Fa - Ffk
    Fnet = Fa - Ffs

    3. The attempt at a solution

    I made Fnet for equation #2 0. I isolated each for force applied for each of the equations and set them equal to each other.

    My equation before plugging numbers in for variables was this:

    Ffk = Fnet + Ffs

    I tried expanding the equation then solving for acceleration in which I got a negative value so I know I did something wrong.

    I'd like to know the logic behind solving this equation and the process itself

    Thanks so much
    Last edited: Oct 6, 2013
  2. jcsd
  3. Oct 6, 2013 #2


    User Avatar

    Staff: Mentor

    Hi Kakateo http://img96.imageshack.us/img96/5725/red5e5etimes5e5e45e5e25.gif [Broken]

    Determine the largest force that can be transferred (via friction) to the top box.
    Last edited by a moderator: May 6, 2017
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