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Friction and tension force- mass

  1. Jul 19, 2009 #1
    Friction and tension force-- mass

    1. The problem statement, all variables and given/known data

    In the real world, ramps aren't frictionless, so I had to drag Brisket up a ramp, slanted at 26.6° from the ground, that had a coefficient of kinetic friction = 0.674. I applied a tension force FR=5060.8N to my pet cow using the rope. Brisket moved up the ramp with an acceleration of magnitude 1.54m/s2. With this information, including friction on the ramp, what is Brisket's mass (in kg)?

    2. Relevant equations
    T= Uk*m*g/cos(angle)+Uksin(angle)
    Fnet= ma


    3. The attempt at a solution

    I attempted to use the first equation

    5060.8 = .674 * m * 9.8 / (cos(26.6)+ .674 sin(26.6)

    using this equation i got 916.31 kg which is incorrect

    any tips would be much appreciated thanks
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jul 19, 2009 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Friction and tension force-- mass

    Where does this formula come from?

    Instead, just analyze the forces acting on the cow and apply Newton's 2nd law:
     
  4. Jul 19, 2009 #3
    Re: Friction and tension force-- mass

    ok so the forces i have acting on the cow are:

    mgsin(angle)
    mgcos(angle)
    mg
    Friction(going up the incline)
    N(force)

    im not sure how to arrive at Fnet because i need the mass to be able to get the components of it
     
  5. Jul 19, 2009 #4

    Doc Al

    User Avatar

    Staff: Mentor

    Re: Friction and tension force-- mass

    The weight (mg) can be broken into components.
    Express the friction in terms of the normal force and μ. Which way does it act?
    Don't forget the tension force.

    Find Fnet by adding up all the force components parallel to the incline. (There are three such components.) Set up an equation using Newton's 2nd law and solve for the mass.
     
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