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Moment of the force

  1. Apr 14, 2012 #1
    1. The problem statement, all variables and given/known data

    Calculate the moment of the force exerted by the crate around support A.

    2. Relevant equations

    crate = 300 kg
    1 kg=10N
    300Kg*10=3000N

    3. The attempt at a solution

    Ra*42 m = 3000N *6m
    Ra = 428,57 N

    Rb*42 m = 3000N *36m
    Rb=2571,42 N


    I just want to check whether my working is correct or not.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

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  3. Apr 14, 2012 #2
    It's easy
     
  4. Apr 14, 2012 #3
    not for every one :C
     
  5. Apr 14, 2012 #4
    It is not easy because you have not been told the size of the box!!!
    The moment of the box = weight x distance of centre of mass from A
     
  6. Apr 15, 2012 #5
    I know only that crate = 300 kg
     
  7. Apr 15, 2012 #6
    My calculation looks like that

    crate = 300 kg
    1 kg=10N
    300Kg*10=3000N

    Ra*42 m = 3000N *6m
    Ra = 428,57 N

    Rb*42 m = 3000N *36m
    Rb=2571,42 N

    MA=3000N*6m-2571,42
    MA=-89999,64

    Ra+Rb=428,57+2571,42=2999,99=3000N!!!

    So the answer is Ra = 428,57 N

    Am I right i thinking?
     
  8. Apr 15, 2012 #7

    PhanthomJay

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    Gold Member

    if you assume that the cm of the crate is at 6 m from the left, your calculations are good, ecept that you should round them off to about 400N and 2600 N, respectively.
     
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