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Problems with Newton's third Law

  1. Mar 6, 2010 #1
    1. The problem statement, all variables and given/known data

    This is more of a concept problem than one of number manipulation. I was wondering, if when a horse pulls forward on a cart with a force of 500 N and the cart pulls back with a force of 500 N by Newton's 3rd Law, how does the cart move if the net force is 0?

    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Mar 6, 2010 #2
    Welcome to Physics Forums.
    The net force on the cart isn't 0 N, it's 500N.
    The Newton 3 reaction force is acting on the horse.
     
  4. Mar 6, 2010 #3
    how it is zero?..
    you said that the horse pulls the cart with a force of 500N , in this case you have a force of 500N acting on the cart ..
    Now, you said that by Newtons third law there should be another 500N force, but pay attention this other force is acting on the horse!! not the cart, so thats why the cart is moving! .. can you see the difference now? .. if not ask again .. :)
     
  5. Mar 16, 2010 #4
    Thanks a bunch, yeah it makes sense now
     
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