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Homework Help: Man/piano problem

  1. Oct 7, 2008 #1
    1. The problem statement, all variables and given/known data
    A 399 kg piano slides 3.6 m down a(n) 27° incline and is kept from accelerating by a man who is pushing back on it parallel to the incline. The effective coefficient of kinetic friction is 0.40. Calculate the force exerted by the man.

    2. Relevant equations

    3. The attempt at a solution

    Ok, I took mg(sin27)-(mu)mg(cos27)=0
    339kg*9.8m/s^2*sin27-0.40*339kg*9.8m/s^2*cos27=0 and got 324N for an answer which is apparently not correct. I tried it several different ways and keep coming up with the same answer. Please help!
  2. jcsd
  3. Oct 7, 2008 #2


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    Bones, welcome to PF!
    you mean = F_applied by man, not 0.
    The problem statement notes the mass as 399 kg, but you used 339 kg!
  4. Oct 7, 2008 #3
    I must be dyslexic because I worked on that problem for hours and didn't notice that once! Thanks ;)
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