question: a hourse is 'bound' together with a cart to carry goods. according to newton's third law,when 2 bodies interact,they exert equal and opposite forces on one another. then,if horse exerts a force to move forward,there should be an equal and opposite direction force exerted by the cart that acting on horse. then net force between these two bodies will be zero. BUT WHY THE HORSE STILL CAN MOVE FORWARD IF THE NET FORCE BETWEEN CART AND HORSE ARE ZERO?