If an object floats, what can be inferred about its density relative to the surrounding fluid?

• A. Higher density than the fluid.
• B. Equal density with the fluid.
• C. Density is not related to buoyancy.
• D. Lower density than the surrounding fluid.

Answer: (D)

When something floats, the buoyant force from the fluid balances the object's weight. That buoyant force equals the weight of the displaced fluid, so to balance weight with only partial submersion, the object must have a smaller density than the fluid. If its density were higher, gravity would pull it down and it would sink. If its density were equal, it would be neutrally buoyant and could stay at any depth, not necessarily float at the surface. Therefore, floating implies the object’s density is lower than the surrounding fluid.