This question was previously asked in

SSC JE ME Previous Paper 11 (Held on:22nd March 2021 Morning)

Option 1 : linear

__Explanation:__

Newtonian fluids:

- It is defined as fluids for which the shear stress is linearly proportional to the shear strain rate
- Newtonian fluids are analogous to elastic solids (Hooke’s law: stress proportional to strain)
- Any common fluids, such as air and other gases, water, kerosene, gasoline, and other oil-based liquids, are Newtonian fluids

Newtonian fluids follow the following Newton's law of viscosity.

\(\tau = \mu \frac{{du}}{{dy}}\)

where, μ is the dynamic viscosity of the fluid

Non-Newtonian fluid:

- Fluids for which the shear stress is not linearly related to the shear strain rate are called non-Newtonian fluids examples include slurries and colloidal suspensions, polymer solutions, blood, toothpaste, Quicksand etc.
- Non- Newtonian fluids do not follow Newton's law of viscosity.

Ideal fluid:

- Fluids which don’t have viscosity and are incompressible are termed as an ideal fluid such fluid do not offer shear resistance i.e no resistance is encountered as the fluid moves.
- These fluids are hypothetical fluids and do not exist in reality.

Compressible fluid:

- Compressibility of any substance is the measure of its change in volume under the action of external forces. Compressible flow is often called as variable-density flow.
- These are the fluids in which significant density variations occur during the flow and with pressure applied i.e., these fluids are sensitive to the change in the pressure.