Buoyancy
Buoyancy is the tendency for materials to sink or rise in a fluid.
Buoyancy is also known as the buoyant force…it is the upward force exerted on objects submerged in fluids (gas or liquid).
The buoyancy principle states that when an object is submerged in a liquid, the object experiences an upward buoyancy force that is equal to the weight of the liquid the object displaced.
The Archimedes Principle states that the buoyant force is equal to the displaced fluid, which in very simple terms mean that the effort needed to keep something afloat will be the same as the effort exerted to spread out the fluid or water volume that it pushes out by its presence.
To keep a dense metal afloat in water, it must displace that mass of water which mass can exert enough force on the metal body. For example, a solid metal will not float in water but a water tight body made of metals will float if the mass of metal is so spread out and it takes up volume to spread out its mass (ships have rooms and empty spaces).
Things that rely on buoyancy to work:
- Moving nutrients in our bloodstream
- Pollen floating through air
- Planes and boats transporting goods
If the average density (the total mass of the substance and everything on it divided by the total volume) is less than the density of the water then it will float.
Average density is useful because it helps objects that would otherwise sink, to float. It can also help floating objects to sink.
• Swim bladder in a fish helps it rise and sink in the water
• Life jackets on a person help us float..it lowers our average density
• The amount of that in a submarine determines if it rises or sinks
• The large volume of a blimp compared to its weight