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Force and Air Resistance

  1. Jun 9, 2007 #1
    1. The problem statement, all variables and given/known data
    If a bicyclist of mass 68.0 kg (including the bicycle) can coast down a 6.90 degree hill at a steady speed of 5.80 km/hr because of air resistance, how much force must be applied to climb the hill at the same speed (and the same air resistance)?


    2. Relevant equations
    The air resistance equations dont seem to apply.

    F=MA as always


    3. The attempt at a solution
    I drew the FBD, tried to sum the forces and got:
    The sum of forces in x= mgsino-Fa (force of air resistance)= ma
    Sum of forces in y= N-mgcoso=0

    Can anyone help me out?
    Thanks
     
  2. jcsd
  3. Jun 9, 2007 #2

    PhanthomJay

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    What is the value of the acceleration in the x direction along the incline, if the bicyclist is moving at steady speed?
     
  4. Jun 9, 2007 #3

    Doc Al

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    Staff: Mentor

    Use the data provided in the downhill case to figure out the magnitude of the air resistance. Then apply that to the uphill case.
     
  5. Jun 10, 2007 #4
    im confused as to which formula i use for air resistance.
     
  6. Jun 11, 2007 #5

    Doc Al

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    Staff: Mentor

    You won't calculate the air resistance directly; instead, you'll deduce it from the fact that the bicyclist moves at a steady speed. What does that tell you about the net force on him?
     
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