Answer:
The acceleration of an air cart, which is an object moving on a cushion of air, would not change when adding mass to it because the force of air resistance acting on the cart is negligible compared to the force applied by the air source that propels it. Therefore, the total force acting on the cart remains almost constant, regardless of the cart's mass, and according to Newton's second law of motion, the cart's acceleration would remain the same. This assumes that the air source provides a constant force and that the added mass does not significantly affect the friction between the cart and the surface on which it is moving.