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Homework Help: How do I find the work and power if I have a mass in newtons?

  1. Mar 27, 2008 #1
    Im trying to find my work when climbing up stairs. If I convert my weight into newtons, do I still need to multiply it by 9.8? Since i weigh 135, I multiplied that by 4.5 to get my weight in newtons. I then multiplied that by 9.8, after that I multiplied that by 3.0 m ( the distance of the stairs). I got a really big number

    that okay?
  2. jcsd
  3. Mar 27, 2008 #2
    Why did you multiply by 4.5? 135 what?
  4. Mar 27, 2008 #3
    135 pounds

    1pound=4.45 newtons
  5. Mar 27, 2008 #4
    So then why did you multiply by 9.8 again if you already have your weight in Newtons?
  6. Mar 27, 2008 #5


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    No, it's not ok. You only put units on the height of the stairs. Put units on EVERYTHING. You weight 135? 135 what? I'm guessing lbs. Don't make me guess. So then 135lb*4.5N/lb=607N is already a force unit (newtons=kg*m/sec^2). I'm guessing when you said 9.8 you mean 9.8m/sec^2. Work is force times distance. Is 607N*9.8m/sec^2 even a force unit? Can you answer your own question? "If I convert my weight into newtons, do I still need to multiply it by 9.8?". Yes or no?
  7. Mar 27, 2008 #6
    no, you dont..

    okay, thanks

    let me change my data

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