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A stick falls.

  1. Feb 3, 2014 #1
    Mod note: deleted image that was way too large.
    1. The problem statement, all variables and given/known data
    I want to know the time flowed while the stick falls.

    gravity = g
    density of the stick is same so it's center of mass is l/2.
    what is the T?

    2. Relevant equations

    3. The attempt at a solution
    failed to do torque.
    Last edited by a moderator: Feb 3, 2014
  2. jcsd
  3. Feb 3, 2014 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    You mean - "how long does it take for the stick to fall?"
    Is the point of contact a fixed pivot?

    ... then learn.
    The subject requires an actual physics lesson - there is no shortcut - lessons are expensive for a reason.

    You need to draw the forces into the diagram.
    At the center of mass, gravity creates a torque.

    Torque is the perpendicular component of the force times the distance.
    In your case, the torque will depend on the angle.

    The equation to solve is ##\sum\tau = I\ddot\theta## ... so you need to know about angular momentum as well. For the stick, pivoted about one end, ##I=mL^2/3## - where L is the length of the stick.
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