Buoyancy is an upward force acted on an object that is immersed in a fluid by the fluid itself. As the depth increases in a fluid, the pressure increases due to the weight of the fluid. Therefore, when an object of a certain height and a different density is immersed in the fluid, the fluid exerts a higher pressure on the bottom part of the object than the upper part where the fluid exerts a lower pressure. The net effect of this pressure difference will be an upthrust—an upward force called buoyancy. The buoyant force is equivalent to the weight of the fluid that is displaced when the object is immersed in it.
Frequently Asked Questions
Is buoyancy a fluid only property?
No, buoyancy exists in solids too. It is quite intuitive if you consider the effects of friction in the case of solids. For example, when you submerge a ball into the water, there will be a buoyant force acting on the ball due to the pressure difference at the top and bottom of the ball. So the ball, being less dense, would naturally come up due to the pressure difference. Water being a continuum imparts a less resistance on the ball and allows it to come up. In the case of a solid medium, say if you put the same ball inside a container full of high-density sand particles, there will absolutely be a buoyant force acting on the ball. But the buoyant force will find it hard to overcome the friction between the sand and the ball. Buoyancy is negligible in solids.