Answer:
The net forces exerted on the the horse and cart are not the same, so they are not balanced forces.
Step-by-step explanation:
According to Newton's 2nd Law, an object accelerates if there is a net or unbalanced force on it. For a body to accelerate, two factors are involved which are the mass of the object and the net force acting upon the body. In this situation, there is just one force exerted on the cart i.e: the force that the horse exerts on it. The cart accelerates because the horse pulls on it. The amount of acceleration can be calculated by dividing the net force on the cart by its mass.
In this scenario, we can clearly see the actions of the pull and push forces. The pull force brings an object closer while the push moves an object away from something. The cart pulls the horse backwards, and the ground pushes the horse forward. They both work in opposite directions. The net force is determined by the relative sizes of these two forces.
If the push force is greater(i.e the ground pushes harder on the horse than the cart pulls), then there is a net force in the forward direction, and the horse accelerates forward. But if the pull force is greater( the cart pulls harder on the horse than the ground pushes), then there is a net force in the backward direction, and the horse accelerates backward.
If the force that the cart exerts on the horse is the same size as the force that the ground exerts, the net force on the horse is zero, and the horse does not accelerate.