Centre of Buoyancy is defined as which of the following?

• A. The average center of downward pressure on a submerged surface.
• B. The average center of upward thrust in the water surface.
• C. The weight of water displaced by the body.
• D. The average center of upward lift from water, located in the chest area.

Answer: (D)

The main concept is that buoyancy is an upward force that acts through a specific point—the center of buoyancy. This point is the centroid of the submerged volume, meaning the buoyant force effectively acts at the center of the displaced water. In many swimming or floating positions, especially with the chest and lungs contributing extra buoyancy, this center lies roughly in the chest area. So describing the center of buoyancy as the average center of upward lift from water located in the chest area captures both the direction of the force and a practical location for a typical body in water. The other statements mix up where the force acts or what determines buoyancy: the weight of displaced water tells you the force’s magnitude, not its point of application, and center of pressure or surface-based ideas don’t identify the actual location of the buoyant force.