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Force to push mass down inclined plane

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

    The angle of the ramp is 30 degrees. The mass is 40 kg. What force must be applied to keep the mass sliding down the ramp at constant velocity. The ramp is frictionless*

    2. Relevant equations
    I have missed the past few lessons in class, so I'm not sure. I do have a bunch of equations, but I have little clue on how to use them for this problem


    3. The attempt at a solution
     
    Last edited: Nov 12, 2012
  2. jcsd
  3. Nov 12, 2012 #2
    Assuming there is no friction, the force required to cause the mass to move at a constant rate is equal to the component of the mass's weight down the 30-degree incline. When this happens, the total net force on the mass is zero as the accelerative force (gravity) is canceled out, and it moves at a constant rate. The component of weight down the ramp is given by the expression mgcos(30). This, the force required is mgcos(30), or (40 kg)(9.8 m/s/s)(.866). It will be directed in the direction opposite the component of gravity down the ramp.
     
  4. Nov 12, 2012 #3

    Delphi51

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    Homework Helper

    You might begin with a review of the forces on a block on a ramp.
    You will need to find the normal force pushing the block against the ramp in order to calculate the friction force. Nice diagram here:
    http://en.wikiversity.org/wiki/Motion_in_two_dimensions
     
  5. Nov 12, 2012 #4
    I got it, thanks guys
     
    Last edited: Nov 12, 2012
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