Question

if action is always equal to the reaction explain how a horse can pull a cart

Answer 1

The opposite forces in Newton's third law are not just equal but must also act on 2 different bodies. So when horse exerts a pulling force on the cart, cart exerts an equal and opposite force on the horse. ... When the wheel of the cart pushes on the ground, friction of the ground pushes the wheel making it roll

Answer 2

Answer:

According to the Newton's third law of motion, the house exerts some force on the card, and the cart exerts an equal and opposite force on the horse. So, at first glance it seems that the action and reaction forces being equal and hence the cart would not move. But it should be noted that it is only the force on the cart which determines whether the card will move or not, and that the force exerted by the cart on the horse affects the horse alone. Thus, if the horse is able to apply a force to overcome the frictional force present, the cart will move. So, to make the cart move the horse bends forward and pushes the ground with its feet. When the forward reaction to the backward push of the horse is greater than the opposing frictional forces of the waves, the cart moves.