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Homework Help: Pig on a Slope

  1. Sep 30, 2009 #1
    I'm having a hard time figuring out the equation for this problem:
    A pig slides down a 40.1 ° incline in twice the time it would take to slide down a frictionless 40.1 ° incline. What is the coefficient of kinetic friction between the pig and the incline?

    Can somebody please help me I'm drawing a blank over here
  2. jcsd
  3. Sep 30, 2009 #2


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    Staff: Mentor

    Welcome to the PF. What are the equations for the frictionless/greased pig scenario? How is the Free Body Diagram (FBD) for the pig modified when there is friction?

    We don't do you work for you here at the PF. Please show us your work so we can help you more...
  4. Sep 30, 2009 #3


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    Homework Helper

    Can you get an expression for the time it will take to slide down without friction? Of course it depends on how high or long the ramp is, so you'll have an h or something in the answer.

    If the unknown letters are bothering you, I suggest you begin with a ramp that is 2 meters high and figure out the acceleration and time. Perhaps you will make a diagram of a block on the ramp with the force of gravity vector on it, then find the component of this force that is along the ramp causing the block to accelerate. Then do the same thing again, only put an h in place of the 2.
  5. Sep 30, 2009 #4
    That's the problem though, they gave me nothing but the angle of the incline and the fact that the pig goes twice as slow with the friction. I am assuming that the equation for the frictionless pig is mgsin(theta) with m= mass, g=gravity. But i don't have mass so I have no idea what to do
  6. Sep 30, 2009 #5
    By the way, I appologize for putting this question in the wrong forum I saw "college physics" underneath the advanced physics part so I instantly just went that way without thinking twice
  7. Sep 30, 2009 #6


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    Homework Helper

    "mgsin(theta)" looks good, but an equation needs an equal sign: what is that expression equal to? Can you draw a diagram of the slope with the force of gravity vector and this mg*sin(A) vector showing? If you do it in a paint program and post it we can help you much more easily. The best approach is to upload the diagram to a site like photobucket and then give us the link to it.
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