Buoyancy, Archimede’s principle and Laws of Floatation
- The tendency of a liquid to exert an upward force on object immersed in it is called buoyancy.
- Buoyant force is an upward force which acts on object when it is immersed in a liquid. It is also called upthrust.
- When two balls made of different metals having different weights but equal volume are fully immersed in a liquid, they will experience an equal upward buoyant force as both the balls displace equal amount of the liquid due to their equal volumes.
When an object is fully or partially immersed in a liquid. It experiences a buoyant force or upthrust, which is equal to the weight of liquid displaced by the object. Archimedes principle is used in designing ships submarines, lactometre, hydrometer, etc.
Laws of Floatation
- Three cases are possible when the body is immersed in the fluid.
- If the weight of the body is greater than the upward force or upthrust by the fluid acting upwards, then the body sinks.
- If the weight of the body is just balanced by upthrust or the weight of the body is just balanced by upthrust, then the body floats fully immersed.
- If the weight of the body is less than the upward force, then the body floats partially immersed. The centre of gravity of a body is that point at which the whole weight of the body appears to act.
2. When a ship enters in a sea from a river, it raise a bit because the density of saline water is higher.
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