The mass of the full cart is greater than the mass of the empty cart, and the boy is pushing with the same force, so the acceleration is less. The force exerted on the cart by the man is greater than the force exerted on the same cart by the boy, so the acceleration is greater.
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larger mass
The mass of the full cart is greater than the mass of the empty cart, and the boy is pushing with the same force, so the acceleration is less. The force exerted on the cart by the man is greater than the force exerted on the same cart by the boy, so the acceleration is greater.