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Homework Help: Forces on a slope

  1. Mar 1, 2008 #1
    A 3 kg mass is moving along a frictioless surface at 17 m/s. It then reaches a slope and starts up it. The slope has an angle of 10º and a small amount of friction. What is the coefficient of friction on the slope if the block slides 4.5 m up the slope before stopping?

    m=3 kg
    v(i)=17 m/s
    v(f)=0 m/s
    d=4.5 m

    a=v/d*v
    F(g)=mg
    F(N)=F(g)cos(theta)
    F(kf)=F(g)sin(theta)
    F(kf)=(mu)(kf)F(N)

    a=64.2m/s^2
    F(g)=29.4N
    F(N)=29.0N
    F(kf)=5.1N

    (mu)(kf)=F(kf)/F(N)
    =5.1N/29.0
    =0.18???

    I can't seem to determine the F(net) equation. I also can't figure out why V(i) and d would be provided if they aren't a necessary part of the F(kf)=(mu)(kf)F(N). Any help making sense of this problem would be great.
     
  2. jcsd
  3. Mar 3, 2008 #2

    Shooting Star

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    Upward along the plane, the force ma = -mgsin(theta) - u*mgcos(theta). After the m cancels out, it's a matter of simple kinematics and vi and d are both needed.
     
  4. May 2, 2008 #3
    i believe what star* says is right. im just here to tell you if you need basics for kinematics, visit my blog!
     
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