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Orifices and Mouthpieces MCQs - Fluid Mechanics

Orifices and Mouthpieces MCQs - Fluid Mechanics: This section contains the multiple-choice questions and answers on the fluid mechanics chapter Orifices and Mouthpieces. practice these MCQs to learn and enhance the knowledge of Orifices and Mouthpieces.

1. What is the purpose of an orifice in fluid mechanics?

1. To measure the flow rate
2. To store fluid
3. To mix fluids
4. To pressurize fluid

Answer: A) To measure the flow rate

Explanation:

An orifice is commonly used to measure the flow rate of a fluid through a pipe by creating a constriction that causes a pressure drop.

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2. Which orifice is used to monitor the flow of liquid from one reservoir to another under the influence of gravity?

1. Submerged Orifice
2. Internal Orifice
3. External Orifice
4. Eccentric Orifice

Answer: A) Submerged Orifice

Explanation:

A submerged orifice is placed below the surface of a liquid reservoir, and flow occurs due to the difference in liquid levels between the upstream and downstream sides. This kind of orifice is widely used for determining flow under gravity.

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3. What is the formula for calculating the discharge (Q) through an orifice based on the area of the orifice (A) and the coefficient of discharge (Cd)?

1. Q = Cd × A
2. Q = A - Cd
3. Q = Cd + A
4. Q = A / Cd

Answer: A) Q = Cd × A

Explanation:

The formula Q = Cd A, where Cd is the coefficient of discharge and A is the area of the orifice, is used to determine the discharge (Q) using an orifice.

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4. What is the primary principle governing the flow through an orifice?

1. Bernoulli's principle
2. Hooke's law
3. Pascal's principle
4. Archimedes' principle

Answer: A) Bernoulli's principle

Explanation:

Flow through an orifice is primarily governed by Bernoulli's principle, which states that in a streamlined flow, an increase in the velocity of a fluid occurs simultaneously with a decrease in pressure.

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5. Which of the following factors affects the discharge of fluid through an orifice?

1. Density of the fluid
2. Viscosity of the fluid
3. Temperature of the fluid
4. All of the above

Answer: D) All of the above

Explanation:

Density of the fluid, Viscosity of the fluid, and Temperature of the fluid are the factors that impact the fluid's behavior and its flow characteristics through the orifice.

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6. Which of the following factors is NOT part of the formula for the coefficient of velocity (Cv)?

1. Pressure of the fluid
2. Theoretical velocity of the fluid
3. Viscosity of the fluid
4. Actual velocity of the fluid

Answer: A) Pressure of the fluid.

Explanation:

The coefficient of velocity (Cv) formula involves the ratio of actual velocity to theoretical velocity and does not directly depend on the pressure of the fluid.

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7. What happens to the coefficient of velocity (Cv) in a perfectly ideal fluid flow?

1. Cv is zero
2. Cv is one
3. Cv is less than zero
4. Cv is greater than one

Answer: B) Cv is one.

Explanation:

In a perfectly ideal fluid flow, where there are no energy losses, the actual velocity equals the theoretical velocity, resulting in a coefficient of velocity (Cv) of 1.8.

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8. Which of the following factors can influence the coefficient of contraction?

1. Temperature of the fluid
2. Density of the fluid
3. Viscosity of the fluid
4. Pressure of the fluid

Answer: A) Temperature of the fluid

Explanation:

The fluid's temperature affects the coefficient of contraction. The flow behavior may change as a result of changes in fluid density brought on by temperature changes.

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9. The formula for calculating the discharge coefficient (Cv) in a pipe is:

1. Cv = Q_actual / Q_theoretical
2. Cv = Q_theoretical / Q_actual
3. Cv = A_actual / A_theoretical
4. Cv = A_theoretical / A_actual

Answer: A) Cv = Q_actual / Q_theoretical

Explanation:

The discharge coefficient (Cv) for a pipe relates the actual flow rate (Q_actual) to the theoretical flow rate (Q_theoretical)

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10. If the actual velocity of the fluid in a nozzle is 35 m/s and the theoretical velocity is 40 m/s, what is the velocity coefficient (Cv)?

1. 0.875
2. 1.2
3. 1.7
4. 0.7

Answer: A) 0.875

Explanation:

Using the formula Cv = Actual Velocity / Theoretical Velocity, Cv = 35 m/s / 40 m/s ≈ 0.875

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11. For a large orifice, the flow velocity profile is best described as:

1. Uniform across the orifice
2. Irregular and turbulent
3. Parabolic across the orifice
4. Inversely proportional to the orifice diameter

Answer: A) Uniform across the orifice

Explanation:

A large orifice has a flow velocity profile almost uniform throughout the orifice. This occurs as a result of the orifice geometry having less of an impact on the flow than smaller orifices.

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12. What is the discharge coefficient for a large rectangular orifice?

1. 0.61
2. 0.98
3. 1.23
4. 1.00

Answer: A) 0.61

Explanation:

The discharge coefficient for a large rectangular orifice is typically taken as 0.61. This coefficient is used to relate the actual discharge through the orifice to the theoretical discharge that would occur if the orifice were a perfect sharp-edged orifice.

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13. A fully submerged orifice with a diameter of 0.5 meters is subjected to a head of 2 meters. Calculate the approximate discharge through the orifice. Use a discharge coefficient of 0.61.

1. 0.152 m³/s
2. 0.248 m³/s
3. 0.412 m³/s
4. 0.685 m³/s

Answer: B) 0.248 m³/s

Explanation:

The discharge through a fully submerged orifice can be calculated using the formula:

Q = Cd * A * √ (2 * g * h)

Where:
Q = Discharge
Cd = Discharge coefficient (0.61)
A = Area of the orifice (π * r²)
r = Radius of the orifice (d/2)
g = Acceleration due to gravity (9.81 m/s²)
h = Head over the orifice (2 meters)
Putting the values:
r = 0.1 / 2 = 0.05 m
A = π * (0.05 m) ² ≈ 0.007853 m²
Q = 0.61 * 0.007853 m² * √ (2 * 9.81 m/s² * 2 m) ≈ 0.248 m³/s

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14. The shape of a mouthpiece that produces the highest discharge coefficient is:

1. Converging
2. Diverging
3. Converging-diverging
4. Cylindrical

Answer: C) Converging-diverging

Explanation:

The converging section accelerates the fluid and decreases pressure, while the diverging section slows down the fluid and allows for pressure recovery. This combination of effects results in improved discharge coefficients compared to simple converging or diverging shapes.

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15. Classification of mouthpieces is based on:

1. Material composition
2. Shape and size
3. Temperature range
4. Surface finish

Answer: B) Shape and size

Explanation:

Mouthpieces are devices used to control the flow of fluids, particularly liquids, from one point to another. Their classification is primarily based on their shape and size, as this factor greatly influences the flow characteristics and efficiency of the device.

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