Question 1: What is the principle behind Bernoulli's Equation?
A) The sum of the pressure, kinetic, and potential energy per unit volume is constant.
B) The flow rate remains constant along a streamline.
C) The velocity of a fluid is directly proportional to its pressure.
D) The velocity of a fluid is inversely proportional to its density.
Explanation: Bernoulli's equation is derived from the conservation of energy principle for flowing fluids, stating that the sum of pressure energy, kinetic energy, and potential energy remains constant along a streamline.
Question 2: What does the continuity equation in fluid mechanics represent?
A) The mass flow rate of an incompressible fluid is constant along a streamline.
B) The pressure of an incompressible fluid is constant along a streamline.
C) The velocity of an incompressible fluid is inversely proportional to its density.
D) The volume flow rate of a compressible fluid is constant along a streamline.
Explanation: The continuity equation states that for an incompressible fluid, the mass flow rate is constant along any streamline, meaning that the velocity and cross-sectional area are inversely proportional.
Question 3: What is the unit of dynamic viscosity?
A) Pascal-second
B) Newton-second per square meter
C) Joule per meter
D) Kilogram per meter per second
Explanation: Dynamic viscosity is measured in Newton-seconds per square meter (N·s/m²), which reflects the fluid's resistance to shear flow.
Question 4: What does the Reynolds number indicate in fluid mechanics?
A) The viscosity of the fluid
B) The flow regime of the fluid, whether laminar or turbulent
C) The speed of the fluid flow
D) The density of the fluid
Explanation: The Reynolds number is a dimensionless quantity that helps predict whether the flow of a fluid is laminar or turbulent. If Reynolds number is below 2000, the flow is laminar; if above 4000, it's turbulent.
Question 5: What is the difference between an ideal and a real fluid?
A) An ideal fluid has no viscosity, whereas a real fluid has zero compressibility.
B) An ideal fluid has no viscosity, whereas a real fluid has viscosity.
C) An ideal fluid can compress, whereas a real fluid is incompressible.
D) An ideal fluid is always in motion, while a real fluid is stationary.
Explanation: Ideal fluids are hypothetical and have no viscosity, while real fluids possess viscosity and experience internal resistance to flow.
Question 6: What is the primary cause of flow separation in a fluid flow around an object?
A) High pressure at the rear of the object
B) High velocity near the object surface
C) A decrease in velocity and an increase in pressure
D) High temperature near the object surface
Explanation: Flow separation occurs when the velocity of the fluid decreases and pressure increases, causing the flow to detach from the surface of the object.
Question 7: In the context of fluid flow, what does the term "shear stress" refer to?
A) The force per unit area acting parallel to the surface of the fluid
B) The force per unit volume acting perpendicular to the surface of the fluid
C) The pressure difference across a fluid layer
D) The resistance to fluid acceleration
Explanation: Shear stress is the force exerted parallel to the surface of the fluid, which causes the layers of the fluid to slide over each other.
Question 8: What is the velocity profile in laminar flow?
A) Parabolic, with maximum velocity at the center and zero at the walls
B) Linear, with constant velocity across the pipe cross-section
C) Uniform, with constant velocity throughout the fluid
D) V-shaped, with the highest velocity near the walls
Explanation: In laminar flow, the velocity profile is parabolic, meaning the velocity is highest at the center of the pipe and decreases towards the walls due to friction.
Question 9: What is the formula for calculating the flow rate in a pipe?
A) Q = A * v
B) Q = π * r² * v
C) Q = ρ * A * v
D) Q = A * P
Explanation: The flow rate (Q) is the product of the cross-sectional area (A) and the velocity (v) of the fluid, or Q = A * v.
Question 10: What is the primary assumption made in the study of ideal fluids?
A) The fluid is incompressible and has no viscosity
B) The fluid moves in a constant direction without acceleration
C) The fluid is perfectly compressible
D) The fluid flows in a straight line with uniform velocity
Explanation: Ideal fluid assumptions include incompressibility and no viscosity, which simplifies fluid flow analysis.
Question 11: What is the unit of flow rate?
A) Cubic meters per second (m³/s)
B) Kilograms per second (kg/s)
C) Newtons per meter (N/m)
D) Meters per second (m/s)
Explanation: Flow rate is measured in cubic meters per second (m³/s), which represents the volume of fluid passing through a given cross-sectional area per unit time.
Question 12: What is the main reason for the formation of vortices in a fluid flow?
A) High-pressure gradients
B) Irregularities in the flow, such as obstacles or sharp bends
C) Low temperature
D) Decreased viscosity
Explanation: Vortices are formed when irregularities like obstacles or sharp bends disturb the flow, causing the fluid to rotate around an axis.
Question 13: Which of the following fluids exhibits no internal resistance to flow?
A) Ideal fluid
B) Real fluid
C) Newtonian fluid
D) Non-Newtonian fluid
Explanation: An ideal fluid is a hypothetical concept that does not exhibit internal resistance to flow, meaning it has no viscosity.
Question 14: What is the effect of increasing the temperature of a fluid on its viscosity?
A) It decreases the viscosity
B) It increases the viscosity
C) It has no effect on viscosity
D) It makes the fluid more compressible
Explanation: For most fluids, increasing temperature reduces viscosity, as molecules move faster and are less resistant to flow.
Question 15: Which flow pattern is characterized by smooth and orderly fluid motion?
A) Laminar flow
B) Turbulent flow
C) Steady flow
D) Unsteady flow
Explanation: Laminar flow is characterized by smooth and orderly fluid motion, where fluid particles move in parallel layers.
Question 16: What is the term for the fluid's resistance to shear deformation?
A) Bulk modulus
B) Viscosity
C) Compressibility
D) Density
Explanation: Viscosity refers to the resistance of a fluid to shear deformation, essentially describing its internal friction.
Question 17: What type of flow occurs when the velocity of the fluid is below a certain threshold and the flow remains smooth?
A) Laminar flow
B) Transitional flow
C) Turbulent flow
D) Steady flow
Explanation: Laminar flow occurs when the fluid moves smoothly, typically at low velocities, where adjacent layers of fluid slide past each other without mixing.
Question 18: What is the relationship between pressure and fluid velocity in a converging pipe according to Bernoulli's principle?
A) As velocity increases, pressure decreases
B) As velocity increases, pressure increases
C) Velocity and pressure remain constant
D) Pressure increases and velocity decreases
Explanation: According to Bernoulli's principle, as the velocity of a fluid increases, its pressure decreases in a converging pipe.
Question 19: Which type of fluid has a constant viscosity independent of the applied shear stress?
A) Newtonian fluid
B) Non-Newtonian fluid
C) Ideal fluid
D) Real fluid
Explanation: Newtonian fluids have a constant viscosity that does not change with the shear rate, unlike non-Newtonian fluids where viscosity varies with shear stress.
Question 20: What is the effect of increasing the pipe diameter on the fluid flow rate, assuming other factors remain constant?
A) The flow rate increases
B) The flow rate decreases
C) The flow rate remains unchanged
D) The flow rate fluctuates
Explanation: As the pipe diameter increases, the cross-sectional area increases, leading to a higher flow rate if the velocity remains constant.
Question 21: What is the principle behind the operation of a venturi meter?
A) The pressure decreases as the velocity of the fluid increases
B) The pressure increases as the velocity of the fluid increases
C) The velocity remains constant across the pipe
D) The density of the fluid increases as the velocity increases
Explanation: The venturi meter works on the principle that the pressure of a fluid decreases as its velocity increases when it flows through a constricted section of pipe.
Question 22: What does the Reynolds number determine in fluid mechanics?
A) The viscosity of the fluid
B) Whether the flow is laminar or turbulent
C) The density of the fluid
D) The pressure drop in a pipe
Explanation: The Reynolds number is used to predict the flow regime; if it is below a critical value, the flow is laminar, and if above, the flow becomes turbulent.
Question 23: Which of the following is the correct formula for Bernoulli's equation?
A) P + ½ρv² = constant
B) P + ρgh = constant
C) P + ½ρv² + ρgh = constant
D) P + ρgh = ½ρv²
Explanation: Bernoulli's equation relates the pressure (P), velocity (v), and height (h) of a fluid in motion, and the sum remains constant along a streamline.
Question 24: In fluid mechanics, what does the term 'streamline' refer to?
A) A path followed by fluid particles
B) A path of least resistance for a fluid flow
C) A line along which fluid velocity is zero
D) A point where fluid pressure is maximum
Explanation: A streamline is the path followed by fluid particles, and at any given moment, the fluid particles do not cross the streamline.
Question 25: What does the term 'viscosity' measure in a fluid?
A) The internal resistance to flow
B) The ability of the fluid to absorb heat
C) The fluid's ability to compress
D) The density of the fluid
Explanation: Viscosity is the internal friction within a fluid that resists its flow, and it increases with the fluid's thickness.
Question 26: What is the main assumption in the theory of ideal fluid flow?
A) Fluid has no viscosity
B) Fluid is incompressible and non-viscous
C) Fluid is always in turbulent flow
D) Fluid has zero density
Explanation: In ideal fluid theory, it is assumed that the fluid is incompressible and has no viscosity, making it an idealized model.
Question 27: What does the term 'fluid dynamics' deal with?
A) The study of non-flowing fluids
B) The study of fluid motion and the forces that cause it
C) The behavior of solid-fluid interactions
D) The study of static fluid properties
Explanation: Fluid dynamics is the branch of fluid mechanics concerned with the motion of fluids and the forces acting upon them.
Question 28: Which of the following describes the flow of a real fluid?
A) It has viscosity and exhibits resistance to shear stress
B) It is incompressible and frictionless
C) It flows without any resistance
D) It follows Bernoulli’s equation exactly
Explanation: Real fluids exhibit viscosity, which causes resistance to shear stress, unlike ideal fluids.
Question 29: What is the main factor that determines whether a fluid flow will be laminar or turbulent?
A) Fluid density
B) Reynolds number
C) Fluid temperature
D) Fluid pressure
Explanation: The Reynolds number is the key factor determining whether the flow will be laminar (smooth) or turbulent (chaotic).
Question 30: In a streamline flow, what can be said about the velocity of the fluid at any point?
A) The velocity is constant along the streamline
B) The velocity is different at every point along the streamline
C) The velocity is only affected by external forces
D) The velocity is zero at every point along the streamline
Explanation: In a streamline flow, the velocity at any point along the streamline is constant, as it is determined by the properties of the fluid at that specific point.
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