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Homework Help: Radial acceleration and gravity

  1. Jan 9, 2010 #1
    This is a very basic question, and not specific to one single homework assignment, but general to many similar types of problems.

    If an object is moving in a wheel (like a ferris wheel), I understand how to determine its radial acceleration. But if a problem simply asks for the objects "acceleration", and doesn't specify radial acceleration, does this imply that the radial acceleration vector should be added to the acceleration due to gravity?

    For example, when the object is at the lowest point on the wheel, its radial acceleration is directed entirely upward, while the acceleration due to gravity is entirely downward. If the radial acceleration happens to be "g" at that point, would this mean that the object is experiencing no acceleration? It seems intuitive, but it could easily be counterintuitive.

    Thanks.

    -Dan
     
  2. jcsd
  3. Jan 9, 2010 #2

    Doc Al

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    Staff: Mentor

    No, you don't add the acceleration due to gravity to anything. The acceleration at the bottom is whatever it is. If the wheel is rotating, then there will be an upward radial acceleration which you can obtain in the usual manner (from the kinematics of circular motion). That's that.

    Note that at any point in its motion, the object may have both a tangential and a radial component of acceleration.
     
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