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Frictional Force and acceleration

  1. Oct 20, 2014 #1
    The problem statement, all variables and given/known data

    The force applied to a cart is 10.5 N. The cart now moves toward the right at an acceleration also toward the right of 1.75m/s2. What are the magnitude and direction of the frictional force?


    The attempt at a solution
    I found that my mass is 6kg. I have F, m, and a, but I am unsure how to find the frictional force.
     
  2. jcsd
  3. Oct 20, 2014 #2

    Doc Al

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    Staff: Mentor

    What forces act on the cart? Draw yourself a free body diagram, then apply Newton's 2nd law.
     
  4. Oct 20, 2014 #3

    Doc Al

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    How did you determine the mass? I assume is was given elsewhere in the problem?
     
  5. Oct 21, 2014 #4
    I found mass by using F=ma
    Force=10.5N
    acceleration=1.75m/s2

    I drew a free body diagram with Force in the positive direction, friction pulling the negative way, and acceleration in the positive direction. Also the Normal force going up and mass*gravity going down.
     
  6. Oct 21, 2014 #5

    Doc Al

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    That won't work. For one thing, Newton's 2nd law should be written as ##\Sigma F = ma##, where ##\Sigma F## stands for the net force. In this problem, all you know are the applied force and resulting acceleration.

    You need to be given the mass; there's not enough information to figure it out. Make sure you've posted the full problem, exactly as it was given.
    Good.
     
  7. Oct 21, 2014 #6
    Oh, I have a mass of 3.23 kg for the cart.
     
  8. Oct 21, 2014 #7

    Doc Al

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    That makes more sense. Now you can figure out the net force.
     
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