Engineering Certification Engineering Certification Thermodynamics & Fluid Mechanics 1 — Questions and Answers
Question 1: Which thermodynamic law states that energy cannot be created or destroyed, only converted from one form to another?
- Zeroth Law
- First Law (Correct answer)
- Second Law
- Third Law
Correct answer: First Law
The First Law of Thermodynamics is the law of conservation of energy: the total energy of an isolated system remains constant.
Question 2: What does the Second Law of Thermodynamics state about heat transfer?
- Heat flows spontaneously from cold to hot bodies
- Heat flows spontaneously from hot to cold bodies (Correct answer)
- All heat can be converted to work
- Entropy of a system always decreases
Correct answer: Heat flows spontaneously from hot to cold bodies
The Second Law states that heat naturally flows from a region of higher temperature to a region of lower temperature, and entropy of an isolated system increases.
Question 3: In fluid mechanics, what does Bernoulli's equation relate?
- Viscosity, temperature, and density
- Pressure, velocity, and elevation in a flowing fluid (Correct answer)
- Reynolds number and flow regime
- Friction factor and pipe roughness
Correct answer: Pressure, velocity, and elevation in a flowing fluid
Bernoulli's equation states that for steady, incompressible, inviscid flow, the sum of pressure energy, kinetic energy, and potential energy remains constant along a streamline.
Question 4: What is the Reynolds number used to determine in fluid mechanics?
- Fluid temperature at a given pressure
- Whether flow is laminar or turbulent (Correct answer)
- The friction force on a submerged surface
- The velocity of sound in a fluid
Correct answer: Whether flow is laminar or turbulent
The Reynolds number (Re = ρvD/μ) is a dimensionless ratio that predicts whether fluid flow will be laminar (Re < 2300) or turbulent (Re > 4000) in a pipe.
Question 5: Which thermodynamic process occurs at constant temperature?
- Isobaric
- Isochoric
- Isothermal (Correct answer)
- Adiabatic
Correct answer: Isothermal
An isothermal process occurs at constant temperature, and for an ideal gas, it follows the relationship PV = constant.
Question 6: What is the continuity equation in fluid mechanics based on?
- Conservation of momentum
- Conservation of mass (Correct answer)
- Conservation of energy
- Newton's third law
Correct answer: Conservation of mass
The continuity equation (A₁V₁ = A₂V₂ for incompressible flow) is derived from conservation of mass — what flows in must flow out for steady-state conditions.
Engineering Certification Engineering Certification Thermodynamics & Fluid Mechanics 1
Which thermodynamic law states that energy cannot be created or destroyed, only converted from one form to another?