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Homework Help: Help with Physics 11 Kinematics.

  1. Feb 12, 2012 #1
    1. The problem statement, all variables and given/known data

    A 5.0kg concrete block accelerates down a 34° slope at 4.2m/s^2. Find the coefficient of friction between the block and the slope.

    2. Relevant equations




    3. The attempt at a solution

    a=(mgsinθ-Ff)/m → Ff=mgsinθ-ma

  2. jcsd
  3. Feb 13, 2012 #2
    Welcome to PF,
    Have you drawn your free body diagram? How did you get your x and y components? The question states that the slope is at a 34° angle to the horizontal, not 30°.

    Hint: Friction force = μN

    Hint 2: Remember to add units to EVERYTHING.
  4. Feb 13, 2012 #3
    Yes, I have drawn a FBD with x and y components that is perpendicular to the ramp.

    I used the Fg to find the x by going Fgsin30°. Which would be the same as Fn.

    Where would I go from this step?
  5. Feb 14, 2012 #4
    Why are you using 30° as your angle when it states in the question that it is 34°?

    Your x component isn't the same as your y component, which would be the normal force (Fn). You must also consider the acceleration of the concrete block in your calculations.
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