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Homework Help: Circular motion with decreasing speed

  1. Jun 28, 2010 #1
    1. The problem statement, all variables and given/known data
    An air race pilot with 54 kg makes a vertical loop with 1200 m of radius, in such a way that the airplane's speed decreases at a constant rate.
    Knowing that the airplane's seat force acting over the pilot is 1680 N at point A and 350 N at point C, determine the airplane's seat force when the airplane is at point B.

    2. Relevant equations

    3. The attempt at a solution

    There are three forces acting over the object: the weight W, the centripetal force Fc and the airplane's seat force F.

    I suppose at point A it's something like this:

    [tex] F_c - W - F_a = 0 [/tex]

    and at point C:

    [tex] F_a - W - F_c = 0 [/tex]

    I'm not really sure if these equations are correct. Substituting what I know I can get the speed at that points. But what should I do then to find the force acting at point B?

    Attached Files:

  2. jcsd
  3. Jun 28, 2010 #2


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    Homework Helper

    Since the airplane's speed decreasing at a constant rate, a tangential force is acting on the pilot in the opposite direction to plane's speed. This force in not affecting on the airplane's seat force on the pilot at A and C, but it affects at B.
    Seat force at A and C is given. From that you can find the velocity of the plane at A and C. From that you can find the retardation produced on the plane.
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