If every action has an equal & opposite reaction, how can a horse pull a cart forward ?
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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