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Torque and normal force

  1. Apr 16, 2015 #1
    I was just curious as why, when drawing a free-body diagram of a board about a pivot with weight on either side of the pivot, we do not consider the corresponding normal forces to those weights(using torque considerations). This question was already asked in another post but was asked a little less clearly.
  2. jcsd
  3. Apr 16, 2015 #2


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    In the free body diagram of the board and weight system, you look at external forces only , the weight forces and pivot support forces. The normal forces of the weights are internal forces and excluded. If you wish , however, you can draw a free body of the board alone , then the forces external to the board become the pivot force and the normal force of the 2 objects acting on the board, and get the same result.
  4. Apr 16, 2015 #3
    thank you.
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