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Homework Help: Normal Force and Static Frictional Force

  1. Jan 29, 2008 #1
    1. The problem statement, all variables and given/known data

    A car (m = 1710 kg) is parked on a road that rises 14.7 ° above the horizontal. What are the magnitudes of (a) the normal force and (b) the static frictional force that the ground exerts on the tires?

    Coefficient of static friction: rubber on dry concrete: 1.0


    2. Relevant equations

    F=ma
    Fs max = coefficient of friction x normal force

    3. The attempt at a solution

    I drew some pictures, but I'm slightly computer illiterate so..sorry. Anyway, not really sure, but here's what I got:

    F= (1710 kg)(9.8 m/s^2)
    F= 16758 N

    Attempt at solution of the normal force:

    16758 N x sin (14.7) = 4252.48 N

    Static Frictional Force:

    (I'm really not sure of this, but I'll go ahead)

    (4252.48 N)(1.0)= 4252.48


    I'm just at my wit's end. I've been trying to figure out this problem for two hours straight. I have to enter my answers in online, and I can only have three significant digits, yet I can't enter in scientific notation, so...I just don't know! Help please!
     
  2. jcsd
  3. Jan 29, 2008 #2
    You're thinking too hard about it. If you figure out the sum of forces you have

    [tex]
    \begin{align*}
    \sum F_x &= f_s - mg\sin\theta = 0\\
    \sum F_y &= F_N - mg\cos\theta = 0
    \end{align*}
    [/tex]​
     
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