Newton's 3rd law and horse cart

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Newton's 3rd law states that every action has an equal and opposite reaction, which raises questions about how a horse can pull a cart. The horse exerts force on the ground, which in turn propels it forward, while the cart also pushes down on the ground with an equal force. When the horse pulls the cart, the tension in the harness connects the forces acting on both the horse and the cart. On a slippery surface, without traction, the horse would struggle to pull the cart, indicating the importance of friction in this interaction. This scenario highlights the role of external forces and traction in the application of Newton's laws.
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If every action has an equal & opposite reaction, how can a horse pull a cart forward ?
 
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because the reaction is on a different body
 
Assuming a steady speed, there's no reactive (related to acceleration) force. The horse pushes on the ground which pushes forwards on the horse. The cart pushes on the ground with pushes backwards with a force equal to the forwarce generated by the ground on the horse. There's a tension equal to this force between the connection from horse to cart. The tension pulls back on the horse and forwards on the cart.
 
Here's something to think about. If the horse and cart were on very, very slippery ice and the horse had no horse shoes, he could not pull the cart forward. What does that suggest?
 

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