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Work done

  1. Mar 27, 2008 #1
    Q: a man(40kg) walks up the stair of 3m high, how much work done by the man?

    wat i think is, the man experienced the gravitational pull, so the man should get a work done of mgh=40*9.81*3 J, is this correct?

    but the answer from the thermodynamic course tutorial Q is 0 J. why?

    2nd Q: a man(40kg) walks up the stair of 3m high n walk down to floor again, how much work done by the man?

    for this Q, i will answer 0 J, because the displacement is 0m.
     
  2. jcsd
  3. Mar 27, 2008 #2
    I disagree with the answer for question 1. Is that the exact question, word for word?
     
  4. Mar 27, 2008 #3
    the question is correct, i copy this from a thermodynamics course student. when i get the answer is 0J, i also felt surprised. how should it b 0J i think. is that the frame of reference the thermodynamics course consider is not same as physics course?
     
  5. Mar 27, 2008 #4
    besides tat, the lecturer for the thermodynamics course is a professor in that subject...
    any idea for that?
     
  6. Mar 27, 2008 #5
    Only work done on something else counts. The man has pushed against the stairs, but those haven't moved, so he has added no energy to anything else.
     
  7. Mar 27, 2008 #6
    in case the Q is asking for the work done by the man, so any relation for the man pushing on the stair?
     
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