Explain why a horse cannot pull a cart and run in empty space
In order to pull a cart, a horse pushes the ground backward with some force. The ground in turn exerts an equal and opposite reaction force upon the feet of the horse. This reaction force causes the horse to move forward.
An empty space is devoid of any such reaction force. Therefore, a horse cannot pull a cart and run in empty space
A horse by itself cannot move in space due to law of inertia and so cannot pull a cart in space.