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Rotational Motion

  1. Mar 16, 2009 #1

    bfr

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    1. The problem statement, all variables and given/known data

    I did a lab today where a weight was tied to a string. The string was wrapped around part of the circumference of a wheel, and then the end was taped down. So, when I let go of the wheel and the weight, the force of gravity on the weight causes the wheel to turn. I have two questions:

    1. Is the angular momentum of the system made up of the wheel and the mass conserved?
    2, Is the tension in the string constant?

    2. Relevant equations

    |Torque|=|F||r|sin(θ)
    Angular momentum=I*[tex]\omega[/tex]

    3. The attempt at a solution

    1. I think it isn't conserved because the force of gravity acting on the mass accelerates the system, making angular momentum not be conserved.
    2. The tension is constant because it equals the mass of the weight times 9.8.
     
  2. jcsd
  3. Mar 16, 2009 #2
    You say "the end was taped down." Do you mean the end of the string was taped down? If so, how did this permit the system to move?

    With regard to the tension in the string, draw some FBDs and write some equations of motion before you jump to a conclusion here.
     
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