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Homework Help: Newtons Second Law force help

  1. Jan 21, 2008 #1
    Hey all, I am new to Physics. Recently changed majors from technical writing to physics for the amount of interest I have in the subject. I have been doing ok but I missed a couple of questions on my last homework and I feel that I should have had somebody check my general solved statements after I finished to make sure that I was correct. Anyways, enough about me!

    1. The problem statement, all variables and given/known data
    What is the greatest acceleration a runner can muster if the friction between her shoes and the pavement is 90% of her weight?

    2. Relevant equations
    F = ma
    .9%*9.8 m/s

    http://img183.imageshack.us/img183/8439/accelerationrn5.png [Broken]

    3. The attempt at a solution
    I figure since the force is her body moving at a constant velocity that the greatest acceleration she could reach would be 8.82 m/s. I also tried to make this using Newtons Second Law of a = Fnet/m but what would the net force be equal to? 90%? Any and all help is appreciated, but please post in user friendly terms as I am not that familiar with heavy physics terms yet as I have seen in some other topics(but not all).
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 22, 2008 #2
    I'm not sure how your paper was graded, but maybe you got it wrong because of a little confusion in units and terminology?

    The force of her movement is her body's mass moving at a constant acceleration, not velocity. Also the greatest acceleration would be 8.82 m/s^2. I can't see a mistake otherwise.
  4. Jan 22, 2008 #3
    Thanks Sarujin, your help is appreciated as well as the corrections to my terms. I see why I go it wrong now.
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