define fluid and buoyant force
Answers
buoyant:Buoyancy refers to a force that arises from the pressure exerted on an object by a fluid (a liquid or a gas). ... You can think of the buoyant force as an upward thrust, a force that moves a body in the upward direction
fluid:A substance that has no fixed shape and yields easily to external pressure; a gas or (especially) a liquid.
Answer:-
FLUID :- In physics, a fluid is a substance that continually deforms (flows) under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas, and to some extent, plastic solids. Fluids are substances that have zero shear modulus, or, in simpler terms, a fluid is a substance which cannot resist any shear force applied to it.
Although the term "fluid" includes both the liquid and gas phases, in common usage, "fluid" is often used as a synonym for "liquid", with no implication that gas could also be present. For example, "brake fluid" is hydraulic oil and will not perform its required incompressible function if there is gas in it. This colloquial usage of the term is also common in medicine and in nutrition ("take plenty of fluids").
Fluids display properties such as:
not resisting deformation, or resisting it only slightly (viscosity), and
the ability to flow (also described as the ability to take on the shape of the container).This also means that all liquids have the property of fluidity.
These properties are typically a function of their inability to support a shear stress in static equilibrium.
Solids can be subjected to shear stresses, and to normal stresses—both compression and tensile. In contrast, ideal fluids can only be subjected to normal, compression stress which is called pressure. Real fluids display viscosity and so are capable of being subjected to low levels of shear stress.
Buoyant Force:-
The upward force that is exerted by a liquid on a body which is submerged in it is known as a buoyant force. Its also known as upthrust. Not only liquids but also gases exert upthrust. Even we are acted upon by upthrust but it's not experienced by us due to our weight which is more than the upthrust due to air.
This is also the reason why balloons filled with gases like Helium and Hydrogen, which are less dense than air, go up as the buoyant force is exerted by air on them. Similarly in vacuum, two objects , irrespective of their masses will fall together if released from the same point as in vacuum, there is no presence of air . Thus no air, no upthrust , which may also be known as Air Resistance.