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Moment about a point

  • Thread starter werson tan
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  • #1
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Homework Statement


for M2 , if i take the moment at pont C , then my ans would be (0.3i) x ((125X(3/5) j +125(4/5) k )= 30j +22.5k
Which is not same with the book which use moment about D . why ? Is the value at the triangle at te upper part incorrect (circle part) ?

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The Attempt at a Solution

 

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  • #2
907
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Picture is too small to read.
 
  • #4
907
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Still too small. Just blow up the diagram.
 
  • #5
haruspex
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If you are taking moments about C then presumably you are considering the force at D. Isn't that in the direction -3/5j+4/5k? And should't the displacement vector be -3i?
 
  • #6
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If you are taking moments about C then presumably you are considering the force at D. Isn't that in the direction -3/5j+4/5k? And should't the displacement vector be -3i?
Ya, I would ended up getting 22.5k +30j . But if I take moment about D , I would get 22.5j+30k... Is it correct???
 
  • #7
haruspex
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Ya, I would ended up getting 22.5k +30j . But if I take moment about D , I would get 22.5j+30k... Is it correct???
No, sorry, I had it wrong. The force at D is in the direction -4/5j+3/5k.
 

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