Final answer:
More force being needed to pull a plug from a full tub is due to the weight of the water and doesn't contradict Archimedes' principle, which relates to buoyant force, not gravitational force.
Step-by-step explanation:
The fact that more force is required to pull the plug in a full bathtub than when it is empty does not contradict Archimedes' principle. Archimedes' principle states that the buoyant force on an object is equal to the weight of the fluid it displaces. When the bathtub is full, the water above the plug adds pressure due to its weight, thereby increasing the force required to pull the plug. However, this is not related to the buoyant force being exerted; it is due to the gravitational force of the water acting on the plug.