Question

The term ‘fluid’ is used for
A. Liquids only
B. Gases only
C. A mixture of liquid and gas only
D. Both liquid and gases

Answer 1

Hint: We must keep in mind that some materials have the property that they cannot handle shear stress/force when the specific material is at rest and these materials deform continuously under the action of these tangential stresses.

Complete step by step answer:
A fluid is a material that can flow and it can take the volume of the container when the fluid is poured in it.
The study of fluids is called fluid mechanics. It can be divided into two forms. The study of fluid at rest is called hydrostatic or fluid static, and the study of fluids in motion is called fluid dynamics. In fluids, the force must be applied perpendicular to the liquid surface because fluids are at rest cannot sustain a tangential force. Fluids are a phase of matter and include liquids, gases, and plasmas. Liquids form a free surface (that is, a surface not created by the container) while gases don’t.

We know that from the above information, we find out that the term ‘fluid’ is used for a mixture of liquid and gas only and the correct option is (D).

Additional information:
A fluid is a substance that continually (flows) under applied shear stress, and they have zero shear modulus. Fluids do not resist permanent deformation; it resists only the relative rate of deformation. Fluids can be based on four factors.
a) Continuity (conservation of mass).
b) Conservation of linear momentum.
c) Conservation of angular momentum.
d) Conservation of energy.

Note:
When we talk about the pressure exerted by the fluid, we must note that unlike solids the fluid at a point in rest can exert pressure in all directions equally. Fluid pressure is a well and good explanation that why pressure is a tensor quantity.