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Homework Help: Non-Uniform Motion in a circle

  1. Jul 7, 2008 #1
    I am a bit confused by this question(see attached image). This has been posted before but im not any further forward. My problems are:

    P1 - has this got the following forces acting on it: Weight, Tension, and Natural reaction force?

    and thus does the equation of motion end up as:

    mr''= -|T|er - (mgcos a)er - (mgsin a)eo + |N|er

    where er and eo are the radial and tangential components respectively

    Then is it a case of gathering the similar terms and resolving in the er direction to get:

    ml0'^2 = mg cos a - |T|

    P2 - is this just experiencing the tension of the string and its own weight?

    Attached Files:

  2. jcsd
  3. Jul 7, 2008 #2

    Doc Al

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    Staff: Mentor

    I'm not clear as to what you are asked to solve for.
  4. Jul 7, 2008 #3
    need to identify the forces acting on each particle using appropriate co-ordinates system and then write the equation of motions for each of particle.
  5. Jul 7, 2008 #4

    Doc Al

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    Staff: Mentor

    (1) Looks like you have tension along the radial direction.
    (2) Which way does the tangential component of gravity act?

    I think it might be a bit clearer if you wrote the radial and tangential equations separately.

    I don't know what you did here.

  6. Jul 7, 2008 #5


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    Science Advisor
    Homework Helper

    Welcome to PF!

    Hi confusedalot ! Welcome to PF! :smile:

    Hint: forget tension etc … try starting with conservation of energy. :smile:
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