Buoyancy: A Brief Discussion
- Nov 22, 2016
- Sudipto Das
Buoyancy is a concept that is developed by Archimedes. This is now known as Archimedes principle. The principle states that a body’s buoyed up by a force which is equal to the weight of fluid displaced by the body.
In simpler words, we can say that buoyancy is the tendency or ability of an object to float in a fluid, that can be a liquid or a gas. Buoyancy happens because the pressure of fluids increases with depth. If you take a dive underwater and go deeper and deeper, you’ll feel that the pressure increases with depth. That’s because the molecules get closer and closer with an increase in depth. Therefore, they hit you more because there’s an increase in pressure. This, in turn creates a force in the upward direction.
Buoyancy= weight of the displaced fluid.
Displacement depends on a number of things such as:
- Size of the body,
- Density of water,
- Speed of movement,
- Degree of muscular contractions.
What happens when an object floats in water?
When an object floats, the downward force of the weight of the object is lesser than that of the upward buoyant force exerted by the water.
When the density of an object is less than that of the density of water (1g/cm3), the object will float.
What happens when an object sinks?
When an object sinks, the weight of the specific object is greater than that of the upward buoyant force exerted by water.
The density of the object is greater than the density of water which is 1g/cm3.
When an object is neutrally buoyant in water, it will have the same density as that of water. In such a case, the object will sink down but it will not touch the bottom.
All the 3 representations are depicted in the image below and you’ll get the point in a jiffy.
Simple explanation through a numerical
Archimedes’ principle states that the weight of the displaced fluid is directly proportional to that of the volume of the displaced fluid.
Say, for example, that the weight of a rock is measured to be of 10N. The measurement is done by suspending the rock by a string with gravity working on it in a vacuum.
It’s then observed that the rock displaces water of weight 3N when it is lowered into water. The force acting on the string after it’s lowered into water would then be-
Thus, you can see that buoyancy can reduce the apparent weight of objects. It’s, therefore easier to move an object from the bottom to the surface rather than take it out of water.
So you see that each and every object experiences a certain degree of buoyant force to a certain extent. Now you know the reason for which a huge ship floats on water: buoyant force. With that, we’ll bring this brief discussion to a close. Hope you had a good read.
Sudipto writes technical and educational content periodically for wizert.com and backs it up with extensive research and relevant examples. He's an avid reader and a tech enthusiast at the same time with a little bit of “Arsenal Football Club” thrown in as well. He's got a B.Tech in Electronics and Instrumentation.
Follow him on twitter @SudiptoDas1993
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