Final answer:
The buoyant force on the hollow ball is 15 newtons, which is equal to the weight of the water it displaces. However, the ball weighs 40 newtons and will sink because its weight exceeds the buoyant force.
Step-by-step explanation:
The question deals with Archimedes' Principle and buoyancy. According to Archimedes' Principle, the buoyant force on an object is equal to the weight of the fluid it displaces.
In this case, the hollow ball displaces 15 newtons of water, so the buoyant force exerted on the ball is 15 newtons.
Since the ball weighs 40 newtons and the buoyant force is only 15 newtons, it will sink because the force of gravity on the ball exceeds the buoyant force, which means the ball is not sufficiently buoyant to float in the water.