alleryStart learning →Why does an object immersed in a fluid feel a net upward force at all?
AFluids always push objects toward the surface
BFluid pressure acts only on lower surfaces
CPressure on the bottom exceeds that on top
DThe object displaces its own weight of fluid
Answer & Solution
Correct answer: C. Pressure on the bottom exceeds that on top
1. Pressure in a fluid increases with depth, since it is h rho g.
2. The bottom face of a submerged object lies deeper than its top face, so it sits at a higher pressure.
3. The upward force on the bottom therefore exceeds the downward force on the top, while the horizontal forces cancel.
4. That difference is the buoyant force, so the mechanism is a pressure difference with depth.
5. Saying fluid pressure acts only on lower surfaces is wrong, because pressure is exerted on every surface of the object.
_Source: OpenStax College Physics (CC BY 4.0), Ch 11 "Fluid Statics", section 11.7 Archimedes' Principle_
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