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Fluid Mechanics MCQs - Kinematics of Fluid Motion
Fluid Mechanics MCQs - Kinematics of Fluid Motion: This section contains the multiple-choice questions and answers on the fluid mechanics chapter Kinematics of Fluid Motion. practice these MCQs to learn and enhance the knowledge of Kinematics of Fluid Motion.
1. What is the primary quantity that describes the fluid flow in kinematics?
- Pressure
- Temperature
- Velocity
- Density
Answer: C) Velocity
Explanation:
Kinematics deals with studying the motion of fluid elements, which is described by their velocity.
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2. Which of the following describes steady flow?
- Velocity varies with time at a fixed point
- Velocity is constant with time at a fixed point
- Velocity varies with position at a fixed time
- Velocity is constant with a position at a fixed time
Answer: B) Velocity is constant with time at a fixed point
Explanation:
In a steady flow, conditions do not change with time at any fixed point.
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3. Which type of flow involves a constant density within the fluid?
- Compressible flow
- Incompressible flow
- Steady flow
- Viscous flow
Answer: B) Incompressible flow
Explanation:
In incompressible flow, density remains constant.
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4. In a two-dimensional flow field, velocity vectors at any point lie within a plane. What is the nature of fluid motion in this case?
- Motion along two orthogonal directions
- Motion in a spiral pattern
- Motion along a single direction
- Motion in a helical pattern
Answer: A) Motion along two orthogonal directions
Explanation:
In a two-dimensional flow field, fluid motion occurs in a plane, and velocity vectors lie within that plane, typically involving two orthogonal directions.
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5. What is the characteristic of three-dimensional flow in fluid mechanics?
- Motion occurs only in one direction
- Flow properties are constant throughout the domain
- Flow properties vary in all three spatial dimensions
- Velocity remains constant at any given point
Answer: C) Flow properties vary in all three spatial dimensions
Explanation:
In three-dimensional flow, fluid properties such as velocity, pressure, and density vary in all three dimensions, making the analysis more complex than lower-dimensional flows.
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6. If the cross-sectional area of a pipe carrying water is reduced by half while the velocity remains constant, how does the discharge (Q) change?
- Q remains constant
- Q doubles
- Q halves
- Q quadruples
Answer: C) Q halves
Explanation:
According to the continuity equation, Q = A × V. If area (A) is halved and velocity (V) remains constant, the discharge (Q) will also halve.
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7. What is the SI unit of discharge (Q) in fluid mechanics?
- m/s
- m³
- m³/s
- kg/s
Answer: C) m³/s
Explanation:
Discharge is the volume of fluid passing through a given cross-sectional area per unit of time, and its SI unit is cubic meters per second m³/s.
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8. How does an increase in pipe diameter affect the discharge (Q) for a given fluid velocity?
- Discharge increases
- Discharge decreases
- Discharge remains constant
- Discharge becomes zero
Answer: A) Discharge increases
Explanation:
Increasing the pipe diameter increases the cross-sectional area (A), which results in a higher discharge (Q) for a given fluid velocity (v).
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9. What does the Continuity Equation describe in fluid mechanics?
- The conservation of momentum in a fluid flow
- The conservation of energy in a fluid flow
- The conservation of mass in a fluid flow
- The conservation of angular momentum in a fluid flow
Answer: C) The conservation of mass in a fluid flow
Explanation:
The Continuity Equation ensures that the mass entering a control volume must equal the mass exiting the control volume in a steady flow.
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10. The Continuity Equation relates which two fluid flow properties?
- Velocity and pressure
- Density and velocity
- Pressure and temperature
- Temperature and density
Answer: B) Density and velocity
Explanation:
The Continuity Equation establishes a relationship between the fluid velocity and its density, ensuring that the product of velocity and the cross-sectional area remains constant along a streamline.
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11. In a two-dimensional flow, the Laplace equation for the velocity potential function (φ) is given by:
- ²φ = 0
- φ = 0
- ∂²φ/∂x² + ∂²φ/∂y² = 0
- ∂φ/∂x + ∂φ/∂y = 0
Answer: C) ∂²φ/∂x² + ∂²φ/∂y² = 0
Explanation:
The Laplace equation for the velocity potential function in a two-dimensional flow is ∂²φ/∂x² + ∂²φ/∂y² = 0. This equation represents the condition for an irrotational flow.
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12. Which of the following is a scalar quantity that represents the strength of the source or sink in potential flow theory?
- Velocity potential function
- Stream function
- Vorticity
- Pressure coefficient
Answer: A) Velocity potential function.
Explanation:
The velocity potential function represents the strength of a source or sink in potential flow theory. It is used to mathematically describe the behavior of fluid flowing into or out of a point.
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13. For a steady two-dimensional flow, if the streamlines and equipotential lines coincide, what can be said about the flow?
- It is irrotational
- It is rotational
- It is compressible
- It is viscous
Answer: A) It is irrotational.
Explanation:
When the streamlines and equipotential lines coincide, it implies that the flow is irrotational (no vorticity) and can be described using a velocity potential function. This is a characteristic of irrotational flow behavior.
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14. What type of flow is described by a non-zero stream function (ψ) and zero velocity potential function (ϕ)?
- Irrotational flow
- Rotational flow
- Incompressible flow
- Steady flow
Answer: B) Rotational flow
Explanation:
In a rotational flow, the streamlines are curved and the fluid particles have rotational motion. A non-zero stream function (ψ) and zero velocity potential function (ϕ) indicate such a flow.
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15. For a two-dimensional incompressible flow, what type of flow is described when both the velocity potential function (ϕ) and the stream function (ψ) are constant?
- Rotational flow
- Irrotational flow
- Vortical flow
- Compressible flow
Answer: B) Irrotational flow
Explanation:
When both the velocity potential function (ϕ) and the stream function (ψ) are constant, it indicates an irrotational flow, where the fluid particles move without any rotation or vorticity.
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16. What is vortex flow in fluid dynamics?
- A type of laminar flow
- A flow pattern where fluid particles move radially outward
- The swirling motion of fluid around a central axis
- A flow pattern characterized by parallel streamlines
Answer: C) The swirling motion of fluid around a central axis.
Explanation:
Vortex flow refers to the circular or swirling motion of fluid around a central point or axis, often creating a rotating pattern.
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17. What is the primary factor responsible for the generation of a vortex flow?
- Viscosity of the fluid
- Pressure difference within the fluid
- Gravity acting on the fluid
- Temperature difference within the fluid
Answer: B) Pressure difference within the fluid.
Explanation:
A pressure difference within the fluid is the main driving force for the creation of a vortex flow. This pressure difference causes the fluid to move in a swirling motion around a central point.
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18. Which type of vortex is generated when fluid flows out of a small opening, such as a drain in a sink?
- Free vortex
- Forced vortex
- Rankine vortex
- Solid body rotation
Answer: A) Free vortex.
Explanation:
A free vortex is created when fluid flows out of a small opening, and the velocity of the fluid decreases with increasing radius while conserving angular momentum.
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19. In a forced vortex, how does the velocity of fluid change with increasing radius from the center?
- Velocity increases linearly
- Velocity remains constant
- Velocity decreases linearly
- Velocity increases exponentially
Answer: C) Velocity decreases linearly.
Explanation:
In a forced vortex, the velocity of fluid decreases linearly with increasing radius from the center due to the conservation of mass and angular momentum. This results in a converging flow pattern.
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20. In a closed cylindrical vessel containing a liquid, which of the following statements is true about the pressure at the same height in different radial positions?
- Pressure is higher at the center of the vessel
- Pressure is higher at the outer edge of the vessel
- Pressure is the same at all radial positions
- Pressure varies quadratically with the radial position
Answer: C) Pressure is higher at the outer edge of the vessel.
Explanation:
In a closed cylindrical vessel containing a liquid at the same height, the pressure is the same regardless of the radial position. This is because the pressure depends only on the height of the liquid column and the density of the liquid, not on the radial position.
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