What is the upward force experienced by a body submerged in a fluid that opposes gravity, giving the sensation of weightlessness in water?

• A. Archimedes' principle of buoyancy
• B. Pascal's law
• C. Bernoulli's principle
• D. Newton's third law

Answer: (A)

Buoyant force is the upward push that a fluid exerts on any object immersed in it, opposing gravity. Archimedes' principle states that this buoyant force equals the weight of the fluid displaced by the body. That’s why things feel lighter underwater—the fluid supports part of their weight. If the object is fully submerged, the net force is its weight minus the buoyant force; if they’re equal, the object is neutrally buoyant and stays submerged without rising or sinking. If the buoyant force is greater, it rises.

The other ideas describe different fluid phenomena: pressure transmission in fluids (Pascal’s law), how speed affects pressure in moving fluids (Bernoulli’s principle), and action-reaction forces (Newton’s third law).