: the upward force exerted by any fluid upon a body placed in it — compare archimedes' principle. When an object is placed in a fluid, the fluid exerts an upward force we call the buoyant force. I THINK IT SHOULD BE BUOYANT FORCE. Buoyancy is the force that causes objects to float. Buoyancy or upthrust, is an upward force exerted by a fluid that opposes the weight of a. Archimedes' principle states that the upward buoyant force that is exerted on a body immersed.