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Homework Help: Reaction force on a leaned beam

  1. Jan 27, 2015 #1
    1. The problem statement, all variables and given/known data
    A beam of 12[kN] is on a smooth floor on one side and on a rough edge on the other.
    The total length of the beam is 10[m].
    What is the reaction on the edge.

    2. Relevant equations
    Moments (torque): F1L1=F2L2

    3. The attempt at a solution
    I drew the forces. the reaction on the floor is vertical and also on the edge since there aren't horizontal forces.
    Moments around point A:
    $$12[kN]\cdot 5\cdot \cos 30^0=R\cdot\frac{4[m]}{\tan 30^0}\rightarrow R=7.5[kN]$$
    In the book it's 6.5, i think it's a mistake

    Attached Files:

  2. jcsd
  3. Jan 27, 2015 #2


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    I agree with 7.5kN.

    Edit: looks like they took the horizontal distance for mg but the distance up the slope for the wall's reaction.
    Edit 2: ... are you sure they wanted the total reaction, not just the normal reaction from the wall?
  4. Jan 27, 2015 #3
    I am almost sure they want the total reaction.
    I leave this problem since i have another one, a little more problematic
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