Forces on a body resting on a liquid – weight vs upthrust When a body is placed over (or on) a liquid, it is subjected to two principal vertical forces: gravitational force (its weight) and the upward hydrostatic thrust (buoyant force). Is this statement true?

Introduction:Understanding the vertical force balance on a body interacting with a fluid underpins floatation, apparent weight, and stability problems. The question asks whether both weight and buoyant force act when a body is placed on or in contact with a liquid at rest.

Given Data / Assumptions:

• Quasi-static conditions; fluid at rest (hydrostatics).
• Body may float partially submerged or rest on a support while touching the liquid.
• No dynamic lift or drag considered.

Concept / Approach:

The body’s weight W acts downward. The fluid exerts an upward pressure distribution over the wetted surface; the resultant is the buoyant (upthrust) force. If the body floats freely, equilibrium requires W = buoyant force. If it is supported (e.g., on a scale), the scale reading equals W − buoyant force, evidencing that both forces are present even without full submergence.

Step-by-Step Solution:

Verification / Alternative check:

Apparent weight experiments show a reading drop when an object is immersed partially—direct proof of a buoyant force acting concurrently with weight.

Why Other Options Are Wrong:

False or conditional statements are inconsistent with hydrostatics; buoyancy does not require full submergence, special fluids, or motion.

Common Pitfalls:

Equating “over” with “above but not touching.” The context here is contact with the liquid; once a wetted area exists, hydrostatic pressure generates an upthrust.

Final Answer:

True