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Determining the weight of an object, given force to move it

  1. Feb 24, 2010 #1
    1. The problem statement, all variables and given/known data
    This is the second part of a problem. In the first problem I determined friction coefficient of an 8N block requiring 2.9 N of force to move is .3625.

    The second part of this problem asks: If a weight is added to the block and it now requires 5.7 N to move both at a constant acceleration, what would the weight of the block be?


    2. Relevant equations
    w=mg
    f=uN
    u=f/N


    3. The attempt at a solution

    I attempted to use the friction coefficient I found in the first problem and set it up as N=f/u. This provided me with the wrong answer.
     
  2. jcsd
  3. Feb 24, 2010 #2

    Doc Al

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    Staff: Mentor

    That method should work just fine, assuming you understand how N relates to the answer they want. Are they asking you to provide the amount of weight added to the block?
     
  4. Feb 24, 2010 #3
    The way the question is set up I believe they want the total weight
     
  5. Feb 25, 2010 #4

    Doc Al

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    Staff: Mentor

    To get the total weight of the block plus whatever was added, the method you showed would be correct.

    The wording of the question seemed a bit ambiguous to me--they could also have been asking for the weight added to the block.
     
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