Identify the principle – upward thrust on immersed bodies When a body is immersed wholly or partially in a liquid, it experiences an upward force equal to the weight of the liquid displaced by the body. This statement is known as:

Introduction:
The foundational rule governing buoyancy is a named principle that relates the upward hydrostatic thrust to the weight of displaced fluid. The question asks the learner to correctly identify that named statement used in almost every floatation and apparent-weight problem.

Given Data / Assumptions:

• Body immersed fully or partially in a liquid at rest.
• Uniform gravity, constant fluid density.
• No flow-induced dynamic lift; purely hydrostatic forces are considered.

Concept / Approach:

Archimedes’ principle states: the buoyant force on a submerged body equals the weight of the fluid displaced by that body. This principle follows from integrating the hydrostatic pressure over the surface and is independent of the body’s own density. The principle of floatation is a related consequence: a floating body displaces an amount of liquid whose weight equals the body’s weight.

Step-by-Step Solution:

Verification / Alternative check:

Weighing an object in and out of water shows an apparent weight loss equal to rho * g * V_displaced, confirming Archimedes’ statement experimentally.

Why Other Options Are Wrong:

Pascal's law: Uniform transmission of pressure in a confined fluid.Principle of floatation: Consequence for floating bodies (buoyant force equals weight), not the general law for any immersion.Bernoulli's theorem and D'Alembert's principle: Address different phenomena (energy and dynamics-to-statics transformation).

Common Pitfalls:

Using “principle of floatation” as a synonym. It is related but not the general statement for any immersion depth.

Final Answer:

Archimedes' principle