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Homework Help: Friction and inclines problem. i need help

  1. Jun 12, 2016 #1
    [moderator note: moved from technical forums, no template]

    this is fun but i am stuck. help! :) the first image states the problem and the second image is my futile attempt at a solution

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    Last edited by a moderator: Jun 12, 2016
  2. jcsd
  3. Jun 12, 2016 #2


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    You need a better free body diagram, showing the forces at the top and bottom of the ladder.
  4. Jun 12, 2016 #3
    Theorem. If a rigid body is in rest then the sum of torques about any point is equal zero and the sum of forces is also equal zero.
    It is convenient to calculate torques about one of two contact points of the ladder and the wall/floor.
  5. Jun 15, 2016 #4
  6. Jun 15, 2016 #5
    can i solve this without torques? i haven't got into torques just yet
  7. Jun 15, 2016 #6


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    No. You have three unknowns, the two normal forces and the angle. So you need three equations. Only two are available from linear force balances in two dimensions, so your third must be from torque balance.
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