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Homework Help: Motion described by differential equations

  1. Nov 7, 2015 #1
    1. The problem statement, all variables and given/known data
    Text from a classical mechanics textbook ( uploaded picture ) shows 2 diff equation describing the motion graphically presented in the uploaded picture. How were these set up?

    2. Relevant equations

    3. The attempt at a solution
    I dont have a slightest clue as how are these equations derived in the first place.

    Attached Files:

  2. jcsd
  3. Nov 7, 2015 #2


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    Education Advisor
    Gold Member

    They can be derived from the constraints on the system.

    If it's moving on a plane, z is constant.
    It's perpendicular to the plane.
    It remains perpendicular to the plane.
    And we can assume it's rolling without slipping.

    You can re-derive everything from those four constraints.
  4. Nov 7, 2015 #3
    So how exactly did they get to those two diff equations? The book just wrote them down. And its the first time im hearing about constraints, read it a while ago though...
  5. Nov 7, 2015 #4

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Please type out the equations; posting sideways-oriented photos will not bring you responses from most helpers.
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