Buoyancy of the Liquid (Upthrust)If a block of wood is held below the surface of water and then released, it immediately rises to the surface. The block rises because it experiences an upthrust (or buoyant force) due to water. All fluids exert an upthrust. When a body is immersed in a fluid, it experiences an upthrust or upward force. This upthrust exerted by a liquid on a body immersed in it is known as buoyancy of the liquid.
Law of FloatationAccording to the law of floatation, a body floats in a liquid if the weight of the liquid displaced by the immersed portion of the body is equal to the weight of the body.