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How is acceleration possible if there is an everpresent equal+opp force?

  1. Jan 3, 2012 #1
    In the situation where a horse pulls a wagon, how is it possible for the horse to accelerate if the wagon is exerting an equal and opposite force? Wouldn't the forces cancel each other out?
  2. jcsd
  3. Jan 3, 2012 #2


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    Acceleration is occurs when part or all of the equal and opposing force is a reaction to that acceleration.
  4. Jan 3, 2012 #3


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    The equal and opposite forces act on different objects. The net force on the wagon is the force of the horse on the wagon less some small friction force on the wagon's wheels, so it accelerates. The net force on the horse is the large friction force between the horses feet and the ground driving it forward, less the smaller force of the wagon on the horse calculated above, so the horse also accelerates forward at the same forward acceleration of the wagon .
  5. Jan 4, 2012 #4
    Remember as PhantomJay pointed out, its the net force that produces the acceleration. Both of which are proportional to one another. If the force of the horse acting on the wagon was equal an opposite to the frictional force acting on the wagons wheels then there is no net force, hence no acceleration.
  6. Jan 4, 2012 #5


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    Nice post, Bugattti.
    By the bye... I love your cowl. :biggrin:
  7. Jan 4, 2012 #6
    eh...my what? :confused: :smile:
  8. Jan 4, 2012 #7


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    Sorry, Pal... I thought that it was self-evident. I love the old Bugatti's, and one of their signature features was a honkin' long cowl (hood) with the flex-pipe headers sticking out.
  9. Jan 4, 2012 #8
    Danger - I knew a fellow long ago that sold a Bugatti Kit for the handyman. Also, I apologize for the off topic comment - it won't happen again
    Last edited: Jan 4, 2012
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