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Inlined plane with friction.

  1. Dec 16, 2009 #1
    1. The problem statement, all variables and given/known data
    phsics.jpg
    I have the weight of a mass (8KG) on a inclined plane(35 degrees) with an applied force going parallel to the plane at 20 N with a µK of .3

    looking for acceleration

    2. Relevant equations
    (8*9.8*(sin(35)-20)/8)


    3. The attempt at a solution
    I got an answer of 200.2 using (8*9.8*(sin(35)-20)/8)

    I'm looking for any equations related to this with out the applied force also or if this is wrong the correct formula
     
    Last edited: Dec 16, 2009
  2. jcsd
  3. Dec 16, 2009 #2

    PhanthomJay

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    I assume the 20 N applied force is pointing up the plane? Are you trying to find the acceleration? Which way does the block slide, up or down? What happened to the friction force? Draw a free body diagram to identify all the forces acting (weight, normal force, friction force, applied force) , then use Newton's laws.
     
  4. Dec 16, 2009 #3
    the friction is .3, it slides up the ramp, I should have drawn that picture better.
     
  5. Dec 16, 2009 #4

    PhanthomJay

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    How can it slide up with a 20 N applied load if gravity alone is pulling it down with a force of mgsintheta = 45 N or so??
     
  6. Dec 16, 2009 #5
    I was taking a stab at the dark with the direction. I'm really bad at this and i haven't been able to find any useful formula on the internet or none seemed useful.
     
  7. Dec 16, 2009 #6

    PhanthomJay

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    Well, I'll catch you a bit later, the block slides down the plane, and you must draw a free body diagram. You have 20N up the plane, 45N down the plane from gravity, and (mu)N from the friction force, acting up the plane, opposing the motion of the block. Add them up with appropriate plus/minus signs and set them equal to 'ma' to solve for a, but first solve for N, the normal force. Also, watch your algebra. Can you calculate the normal force which acts up on the block, perpendicular to the plane? And by the way, welcome to PF!
     
    Last edited: Dec 16, 2009
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