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Homework Help: Find frictional force given acceleration, grade, and mass

  1. Sep 29, 2012 #1
    a 1000 kg car is moving down a road with slope (grade) of 15% while slowing down at a rate of 3.7m/s^2 .What is the direction and magnitude of the frictional force?(define positive in the forward direction)


    Using f=ma

    I have the mass 1000 kg, the acceleration 3.7m/s^2, and slope 15%

    Would my force be the tangent of the angle 15??
     
  2. jcsd
  3. Sep 29, 2012 #2

    SammyS

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    Without working the problem, I say no. For one thing the units are incorrect.
     
  4. Oct 1, 2012 #3
    Sorry these were the numbers, I accidently mixed two probs together:/


    a 1892kg car is moving down a road with slope (grade) of 12% while slowing down at a rate of 3.7m/s^2 .What is the direction and magnitude of the frictional force?(define positive in the forward direction)


    Using f=ma

    I have the mass 1000 kg, the acceleration 3.7m/s^2, and slope 15%

    Would my force be the tangent of the angle 15??
     
  5. Oct 1, 2012 #4
    So basically given this problem:


    a 1892kg car is moving down a road with slope (grade) of 12% while slowing down at a rate of 3.7m/s^2 .What is the direction and magnitude of the frictional force?(define positive in the forward direction)

    Would my force be the tangent of the angle 12??
    With f=ma
     
    Last edited: Oct 1, 2012
  6. Oct 1, 2012 #5

    SammyS

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    The net force will be in a direction parallel to the ramp (down the ramp).

    If the ramp makes an angle of θ with respect to the horizontal, then tan(θ) = 0.12 .

    Draw a free body diagram.
     
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