EIT Fluid Mechanics 1 — Questions and Answers
Question 1: What does Bernoulli's equation express?
- Conservation of mass
- Conservation of momentum
- Conservation of energy along a streamline (Correct answer)
- Newton's second law for fluids
Correct answer: Conservation of energy along a streamline
Bernoulli's equation expresses conservation of energy along a streamline: P + ½ρv² + ρgh = constant.
Question 2: The Reynolds number Re = ρvD/μ classifies flow as turbulent when Re exceeds approximately:
- 500
- 2300 (Correct answer)
- 10000
- 100000
Correct answer: 2300
Flow in a pipe transitions from laminar to turbulent when Re exceeds approximately 2300.
Question 3: What is the SI unit of dynamic viscosity?
- m²/s
- Pa·s (Correct answer)
- N/m
- kg/m³
Correct answer: Pa·s
Dynamic viscosity μ has SI units of Pascal-seconds (Pa·s), equivalent to N·s/m².
Question 4: For a fluid at rest, pressure varies with depth according to:
- P = ρgh (Correct answer)
- P = ½ρv²
- P = μ(dv/dy)
- P = E/V
Correct answer: P = ρgh
In a static fluid, pressure increases with depth as P = ρgh, where h is depth below the free surface.
Question 5: The continuity equation for incompressible flow states:
- ρ₁A₁v₁ = ρ₂A₂v₂
- A₁v₁ = A₂v₂ (Correct answer)
- P₁ + ½ρv₁² = P₂ + ½ρv₂²
- τ = μ(dv/dy)
Correct answer: A₁v₁ = A₂v₂
For incompressible flow, the continuity equation simplifies to A₁v₁ = A₂v₂ (conservation of volume flow rate).
Question 6: What is the buoyant force on an object submerged in a fluid?
- Equal to the weight of the object
- Equal to the weight of fluid displaced (Correct answer)
- Equal to the surface area times pressure
- Equal to the density of the object times gravity
Correct answer: Equal to the weight of fluid displaced
Archimedes' principle states the buoyant force equals the weight of the fluid displaced by the object.
EIT Fluid Mechanics 1
What does Bernoulli's equation express?