What is buoyant force?

What is buoyant force?

• A. The downward force due to gravity.
• B. The upward force exerted by a fluid on an immersed object.
• C. The frictional force between a solid and a liquid.
• D. The pull of magnetic field on a metal.

Answer: (B)

Buoyant force is the upward push that a fluid gives to a body immersed in it. It comes from fluid pressure: pressure increases with depth, so the pressure under the object pushes up harder than the pressure above pushes downward, creating a net upward force. According to Archimedes’ principle, this upward force equals the weight of the fluid that the object displaces, which can be written as density of the fluid times gravity times the submerged volume. This means the buoyant force depends on how much fluid is displaced and how heavy that fluid is, not on the object’s weight alone. That’s why a submerged or partially submerged object experiences an upward buoyant force, and why it rises or floats when this force approaches or exceeds the object’s weight. The other options aren’t correct: gravity is the downward force on the object, friction is a tangential interaction that resists motion in the fluid, and magnetic pull has no role in buoyancy.

Buoyant force is the upward push that a fluid gives to a body immersed in it. It comes from fluid pressure: pressure increases with depth, so the pressure under the object pushes up harder than the pressure above pushes downward, creating a net upward force. According to Archimedes’ principle, this upward force equals the weight of the fluid that the object displaces, which can be written as density of the fluid times gravity times the submerged volume. This means the buoyant force depends on how much fluid is displaced and how heavy that fluid is, not on the object’s weight alone.

That’s why a submerged or partially submerged object experiences an upward buoyant force, and why it rises or floats when this force approaches or exceeds the object’s weight. The other options aren’t correct: gravity is the downward force on the object, friction is a tangential interaction that resists motion in the fluid, and magnetic pull has no role in buoyancy.