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Homework Help: Applications of Newtons Laws (friction)

  1. Sep 30, 2009 #1
    1. The problem statement, all variables and given/known data

    At the airport, you pull a 18-kg suitcase across the floor with a strap that is at an angle of 45 deg above the horizontal. Find

    a) Normal force and

    b) the tension in the strap, given that the suitcase moves with constant speed and that the coefficient of kinetic friction b/w the suitcase and the floor is 0.38.

    2. Relevant equations

    N + mg +fk+ f = ma

    I'm not sure if this equation is correct because they don't give you an initial force...

    Y comp: N-mg + Fsin(theta) = 0

    3. The attempt at a solution

    I just need to know if my equations are right because the don't give an initial force. help?
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 30, 2009 #2


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    Homework Helper

    I like "Y comp: N-mg + Fsin(theta) = 0".
    I think you'll have to write a force equation like that for the horizontal part, too.
    Likely you'll have two unknowns N and F, which you can solve for when you have the two equations.
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