Buoyant force

Definition

Buoyant force is the upward force exerted by a fluid on an object submerged in it. This force opposes the weight of the object and is responsible for making objects float.

5 Must Know Facts For Your Next Test

1. Buoyant force is calculated using Archimedes' Principle: $F_b = \rho_{fluid} V_{displaced} g$, where $\rho_{fluid}$ is the fluid density, $V_{displaced}$ is the volume of displaced fluid, and $g$ is the acceleration due to gravity.
2. The buoyant force does not depend on the depth of immersion but only on the volume of fluid displaced.
3. An object will float if its average density is less than that of the fluid; it will sink if its density is greater.
4. The magnitude of buoyant force experienced by an object submerged in a fluid is equal to the weight of the fluid displaced by that object.
5. Neutral buoyancy occurs when an object's weight equals the buoyant force, causing it to remain suspended in the fluid.

Review Questions

• What factors determine the magnitude of buoyant force acting on a submerged object?
• How does Archimedes' Principle relate to calculating buoyant force?
• Explain why an object with a density greater than that of water sinks while one with lesser density floats.

Related terms

Archimedes' Principle:

$\text{A principle stating that a body immersed in a fluid experiences an upward force equal to the weight of the fluid it displaces.}$

Density:

$\text{A measure of mass per unit volume. It determines whether an object will sink or float in a given fluid.}$

Hydrostatic Pressure:

$\text{The pressure exerted by a stationary fluid at equilibrium due to the gravitational pull on it.}$