What term describes the upward force acting on an object submerged in a fluid?

The term that accurately describes the upward force acting on an object submerged in a fluid is upthrust. Upthrust, or buoyant force, arises due to the pressure differences in the fluid surrounding the submerged object. When an object is placed in a fluid, it displaces a volume of that fluid, and the pressure exerted by the fluid on the bottom of the object is greater than the pressure on the top. This pressure difference results in an upward force that opposes the weight of the object, explaining why objects can float or seem lighter in water.

Buoyancy, while commonly used interchangeably with upthrust, technically describes the overall ability of an object to float or rise in a fluid, rather than specifically naming the force itself. Lift is a term typically used in the context of aerodynamics, referring to the force that acts on an aircraft wing due to air pressure differences and is contextually different from forces acting on submerged objects. Thrust refers to a forward force produced by engines or propellers, which is not relevant in the context of an object submerged in fluid. Thus, upthrust is the most precise term for the upward force experienced by such objects.