Q1: Reynolds number is the ratio of

ANS:B - inertial forces to viscous forces.

Reynolds number (Re) is the ratio of inertial forces to viscous forces.

Explanation:

1. Definition of Reynolds Number:
   • Reynolds number (Re) is a dimensionless quantity used to predict flow patterns in different fluid flow situations. It is defined as: Re=ρ⋅V⋅Lμ\text{Re} = \frac{\rho \cdot V \cdot L}{\mu}Re=μρ⋅V⋅L​ where:
     • ρ\rhoρ is the density of the fluid,
     • VVV is the velocity of the fluid relative to the object,
     • LLL is a characteristic length (such as diameter of a pipe),
     • μ\muμ is the dynamic viscosity of the fluid.
2. Significance of Reynolds Number:
   • Reynolds number helps in determining the type of flow (laminar or turbulent) around an object or through a pipe. It indicates the relative importance of inertial forces (which tend to cause the fluid to accelerate and change direction) compared to viscous forces (which resist the flow and dissipate energy as heat).
3. Interpretation:
   • Reynolds number is dimensionless and is used to classify fluid flow:
     • Laminar flow occurs at low Reynolds numbers (Re < 2000 approximately), where viscous forces dominate and the flow is smooth and orderly.
     • Turbulent flow occurs at high Reynolds numbers (Re > 4000 approximately), where inertial forces dominate, and the flow is chaotic and irregular.
     • Transitional flow occurs in the range between laminar and turbulent regimes.
4. Conclusion:
   • Therefore, Reynolds number (Re) is specifically defined as the ratio of inertial forces to viscous forces within a flowing fluid, providing critical information about the flow regime and behavior.