Buoyancy | Archimedes Principal | Examples & its Calculation

By | January 5, 2019

What is buoyancy?

Buoyancy is the force exerted by a fluid on a body which is wholly or partially immersed in it.

How buoyancy force is calculated?

Magnitude of buoyancy force is calculated on the basis of Archimedes principal.

What is Archimedes principal (or Law)?

The magnitude of buoyancy force acting on a body is always equal to weight of fluid displaced by it.


What are examples of buoyancy?

  • Ships floating on sea water
  • We feel lighter when we enter in water pond
  • Stones inside water seems lighter than they are outside
  • Cork floating in water

How do you calculate buoyancy?

Follow following steps to calculate buoyancy.

  1. Find volume of body submerged
  2. Find weight of equal volume of fluid displaced
  3. The weight of fluid calculated is the buoyancy

What causes buoyancy?

Buoyancy is caused by the difference in pressure acting on the both the sides (up and down) of the body.

How does volume affect buoyancy?

Buoyancy force is directly related to the volume of fluid displaced hence, greater the displaced fluid volume, greater would be the buoyancy.

Does air have buoyancy force?

Yes, air has buoyancy force but it is very weak as compared to water because air has low weight density.

How does shape affect buoyancy?

Yes, a body should have a shape that helps in displacing maximum volume of water to obtain maximum buoyancy. For example, steel, when in the shape of a solid brick, it will sink in water but when it is in the form of a hollow vessel, it will float.

How does weight affect buoyancy?

It is all about volume of fluid displaced which decides buoyancy force acting on a body. But yes, if the weight of floating body is more than it will certainly help in nullifying the effect of buoyancy.

Why is buoyancy important?

Buoyancy is important because it helps ships in floating and it also helps us in swimming.

Does gravity affect buoyancy?

Yes, because buoyancy depends on weight of fluid displaced and we all know weight is a function of gravitational acceleration. Hence in the absence of gravity buoyancy force would be zero.

What causes the buoyancy of a hot air balloon?

The difference in weight density of air inside and outside the balloon creates buoyancy. Hot air inside balloon has less density compared to cold air outside.

Does viscosity affect buoyancy?

Not directly, it is all about volume of fluid displaced. But since for the same fluid, heated fluid will have less viscosity and less weight density so it will have less buoyancy too.

What can affect buoyancy?

  • Acceleration due to gravity
  • Volume of fluid displaced
  • Density of the fluid

What material has the most buoyancy?

Materials which have less density are more buoyant.

Does size affect buoyancy?

As mentioned above size of a material does not affects buoyancy but its shape does. For example, steel in the shape of a hollow vessel will have more buoyancy compared to a steel billet of same size.

How does density affect buoyancy?

Yes, buoyancy is directly proportional to buoyancy. An increase in density of fluid will result in increase in buoyancy.

Can buoyancy be greater than weight?

Yes, in case of hot air balloon.

Does water depth affect buoyancy?

Normally buoyancy does not change with depth unless the body is compressible. For a compressible body buoyancy will decrease with increasing depth.

Why is salt water more buoyant?

Because of more weight density salt water is more buoyant than normal water.

Do objects float better in saltwater or freshwater?

As explained above objects float better in salt water.

Also read:

What are application areas of fluid mechanics?

What is capillary effect?

What are different types of fluid flows?

Examples of fluid

Featured image attributions:┬áBy Yupi666The original uploader was Pbroks13 at English Wikipedia. – [1], CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=4171508



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