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Homework Help: Quick homework question

  1. Apr 2, 2009 #1
    1. The problem statement, all variables and given/known data

    A 100kg block is pulled at a constant speed of 5.0 m/s across a horizontal floor by an applied force off 122N directed 37 degrees above the horizontal. What is the rate at which the force does work on the block?

    2. Relevant equations

    I know here we will use the instantaneous power formula P=dW/dt or P=Fvcos

    3. The attempt at a solution

    well i drew the FBD and started plugging in numbers in my formula, its just im not sure where the Mass falls into place here I know the answer is 4.9x10[tex]^{}2[/tex] watts but not sure where to go from here thanks
  2. jcsd
  3. Apr 2, 2009 #2


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    Homework Helper

    In this problem mass is not needed.
  4. Apr 2, 2009 #3
    well my answer just doesnt match up with the answer my teacher gave us and i dont know why.... i did 122*5.7sin(37) and came up with 418.5W or 4.2X10^2 W
  5. Apr 2, 2009 #4


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    Homework Helper

    Your calculation is wrong.
    122*5*cos(37) = ?
  6. Apr 2, 2009 #5
    wow! the whole time i was using 5.7m/s instead of 5m/s careless mistake sorry to waste your time
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