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Basic physics questions work and energy

  1. Feb 6, 2012 #1
    1. The problem statement, all variables and given/known data

    the man having the weight of 75kg is able to run up a 4.5 m high flight of stairs in 4s. determine the power generated. how long would a 100w light bulb have to burn to expend the same amount of energy?

    2. Relevant equations



    3. The attempt at a solution
    I havnt done these types of questions for a while so ive forgotten, so far ive calculated the work done by weight -75*9.81 (4.50) = -3310.8
    can anyone help me solve the rest pleasE?
    thanks
     
  2. jcsd
  3. Feb 6, 2012 #2

    NascentOxygen

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    Staff: Mentor

    Power = rate of doing work
     
  4. Feb 6, 2012 #3
    yea but i dont know how to do it
     
  5. Feb 6, 2012 #4

    NascentOxygen

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    Staff: Mentor

    How much work is done in 4 seconds?
     
  6. Feb 6, 2012 #5
    power=f.v but i dont know how to get the v and f?
     
  7. Feb 6, 2012 #6

    NascentOxygen

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    Staff: Mentor

    As you know how much work was done in 4 secs, then divide by 4 secs and you have power!

    Also, don't forget work = energy
     
  8. Feb 6, 2012 #7
    Ok thanks
     
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