Question

explain if every action is equal reaction why horse can pull a cart

Answer 1

according to the law the gravitational force acts on the lower and upper direction so it gets nullified out!! the horse uses its mass and force to move the cart there is a less force acting in the opposite direction !! so the horse can pull a cart

Answer 2

A horse pushes the ground backward direction. according to Newton's third law of motion, a reaction force is exerted by the earth on the horse in the forward direction. as a result the cart moves forward