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Homework Help: This is how I solved this friction problem

  1. Sep 18, 2009 #1
    1. The problem statement, all variables and given/known data

    Wooden wall & block. Block=1kg. Block is pressed against the wall by force of 12N's on its lower edge from horizontal 20 degrees.

    Will the block stay, go up, or slide down

    2. Relevant equations

    3. The attempt at a solution

    Fnet = 12xsin30 - 9.8x1kg = -3.8

    so block will slide down

    should I have used wood friction constants too?

    I don't know how to apply wood Uk Us. The block is press hozintally how would kinetic and static frictions affect vertical movement
  2. jcsd
  3. Sep 18, 2009 #2

    Hey there SELFMADE :smile:

    Perhaps you could post the enire question as it was stated? I am a little confused about what is being asked.

    Were you given values of U_k and U_static in the problem?
  4. Sep 18, 2009 #3
    Is it clear now?

    http://img198.imageshack.us/img198/7676/pfsb.png [Broken]

    U_k and U_s aren't given but I figure since a table of coefficients was given in the chapter and problem specifically states "wood" it must be used.
    Last edited by a moderator: May 4, 2017
  5. Sep 18, 2009 #4
    Ok. The problem with your approach is that no, you did not include the effects of friction.

    I suggest that you draw a free-body diagram with all of the forces that are acting on the block.
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