Final answer:
The buoyant force on an object is equal to the gravitational force of the fluid displaced due to Archimedes' principle, which dictates that the weight of the displaced fluid provides an upward force on the object.
Step-by-step explanation:
The reason why the buoyant force on an object is equal to the gravitational force of the fluid displaced is explained by Archimedes' principle. When an object is submerged in a fluid, it displaces a certain volume of that fluid. The displaced fluid has weight, and this weight is supported by the surrounding fluid, resulting in a net upward buoyant force on the object. This force equals the weight of the displaced fluid and acts against the force of gravity on the object. If the buoyant force is greater than the object's weight, the object will float. Conversely, if the buoyant force is less than the object's weight, the object will sink. However, if both forces are equal, the object will remain neutrally buoyant, suspended within the fluid.