Question

An ideal fluid is:
A. Similar to a perfect gas.
B. Non-viscous and incompressible.
C. One which satisfies the continuity equation.
D. One which obeys Newton’s law for viscosity drag.

Answer 1

A fluid is a substance that can flow and take the shape of any container. Here, we will discuss the properties of an ideal fluid to arrive at the answer. An ideal fluid does not exist but all the fluids are actually the real fluids.

Complete answer:
The properties of an ideal fluid are given by
Incompressibility:
The density of an ideal fluid always remains constant regardless of the external pressure applied to the fluid. This the property of compressibility. Therefore, the ideal is incompressibility.
Bulk modulus:
The bulk modulus of an ideal fluid means that there is a decrease in the volume of the fluid with an increase in the pressure of the fluid. Now, as the bulk fluid is incompressible, that is the density is zero, the bulk modulus is zero.
Viscosity:
Viscosity is the property of the fluid which opposes the relative motion of the fluid between the different layers. An ideal fluid is non-viscous which means that an ideal fluid has no internal friction.
Surface tension:
Surface tension means is the property of the fluid which means that the liquid will tend to acquire the minimum surface required. For an ideal fluid, the surface tension is zero.
Irrotational:
An ideal fluid is irrotational in nature which means that the fluid flows with zero turbulence and the particles of the fluid do not rotate about their axis.

Therefore, an ideal fluid is a fluid that is incompressible, irrotational, and non-viscous in nature.

Hence, option B is the correct option.

Note: There are many applications of the properties of an ideal fluid. The most common application of an ideal fluid is in the continuity equation and the Bernoulli equation.
The fluids like water and air are considered an ideal fluid because they have a very low value of viscosity.