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buoyancy

Primary Information
Secondary Information

Definition

Buoyancy is the upward force exerted by a fluid that opposes the weight of a partially or fully immersed object.

Buoyancy is caused by the difference in pressure between the top and bottom of an object that is submerged in a fluid. The pressure at the bottom of the object is greater than the pressure at the top of the object. This difference in pressure creates a force that pushes the object upwards.

The amount of buoyancy depends on the following factors:

  • The volume of the object: The greater the volume of the object, the greater the buoyant force.
  • The density of the fluid: The denser the fluid, the greater the buoyant force.
  • The weight of the object: The greater the weight of the object, the greater the force of gravity pulling it down.
  • If the buoyant force is greater than the weight of the object, the object will float. If the weight of the object is greater than the buoyant force, the object will sink.

Here are some additional details about buoyancy:

  • Archimedes' principle: Archimedes' principle states that the buoyant force on an object is equal to the weight of the fluid that the object displaces.
  • Pascal's law: Pascal's law states that the pressure exerted by a fluid at any point in the fluid is transmitted equally in all directions throughout the fluid.

How can the word be used?

The buoyant force of the water lifted the object up.

buoyancy

Different forms of the word

Noun: buoyancy.

Adjective: buoyant.

Adverb: buoyantly.

Verb: to buoy.

Plural: buoyancies.

Etymology

The word "buoyancy" comes from the Middle French word bouance, which means "buoyantness." The Middle French word bouance is thought to be derived from the Old French word boüant, which means "to float.".

Question

Explain why certain materials float.

AQA Science Exam Question and Answer

Question:

A cork floats in water, but a steel nail sinks. Why?

Answer:

The cork floats in water because the buoyant force on the cork is greater than the weight of the cork. The buoyant force is equal to the weight of the water that the cork displaces. The cork displaces more water than the steel nail because the cork has a larger volume. The steel nail sinks because the weight of the steel nail is greater than the buoyant force on the nail.

The density of the cork is less than the density of water. The density of the steel nail is greater than the density of water. The density of a substance is the mass of the substance divided by the volume of the substance.

The buoyant force is calculated using the following formula:

Buoyant force = weight of the water displaced.

The weight of the water displaced is calculated using the following formula:

Weight of the water displaced = density of water * volume of the object displaced.

Therefore, the buoyant force on an object is greater if the object has a larger volume and if the object is less dense than the fluid.