Fluid Dynamics MCQ with answer and solution

Concept

Bernoulli's equation assumes ideal (non-viscous), incompressible, steady and irrotational flow along a streamline.

Formula

p/(ρg) + V²/(2g) + z = constant

Step-by-step solution

1. List the assumptions of Bernoulli's equation: ideal fluid, incompressible, steady flow, irrotational flow, flow along a streamline. 2. Check each option against these assumptions. 3. Only 'incompressible fluids' matches the assumptions. 4. So the answer is A.

Explanation

Bernoulli's equation comes from Euler's equation and assumes the density is constant, so the fluid must be incompressible. It also assumes no viscosity (no friction loss) and irrotational flow. So it applies to incompressible fluids.

Why the other options are wrong

B: Viscous fluids have friction losses, which Bernoulli's equation ignores. C: Compressible fluids have changing density, but Bernoulli assumes constant density. D: The standard form assumes irrotational flow, not rotational flow.

Shortcut

Bernoulli = ideal + incompressible + steady + irrotational + along a streamline.

Common mistake

Thinking Bernoulli's equation applies to real viscous flow without adding a head loss term.