When a horse pulls a cart, what is the force that helps the horse move forward?
When a horse exerts a force on cart , the cart exerts an equal and opposite force on the horse. Then how come the horse can manage to pull the cart ?
A horse is harnessed to a cart. If the horse tries to pull the cart, the horse must exert a force on the cart. By Newton's third law the cart must then exert an equal and opposite force on the horse. Since the two forces are equal and opposite, they must add to zero, so Newton's second law tells us that the acceleration of the system must be zero and therefore no matter how hard the horse pulls, it can never move the cart.