Fluid Mechanics: Pressure Concepts
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Questions and Answers

What are the units of pressure in the SI system?

  • kg/m<sup>2</sup> (correct)
  • N/m<sup>2</sup> (correct)
  • kg/s<sup>2</sup>
  • m/s<sup>2</sup>

    • What is the relationship between absolute pressure (Pabs), gage pressure (Pg), and atmospheric pressure (Patm)?

  • P<sub>abs</sub> = P<sub>g</sub> + P<sub>atm</sub> (correct)
  • P<sub>atm</sub> = P<sub>abs</sub> - P<sub>g</sub>
  • P<sub>atm</sub> = P<sub>g</sub> - P<sub>abs</sub>
  • P<sub>abs</sub> = P<sub>g</sub> - P<sub>atm</sub>

    • Which of the following units is NOT a common unit for pressure?

  • kg/s (correct)
  • kgf/cm<sup>2</sup>
  • lbf/ft<sup>2</sup>
  • 10<sup>3</sup> Pa

    • What is the pressure at a point in a stationary fluid called?

    <p>Static pressure (B)</p> Signup and view all the answers

    What is the relationship between pressure and depth in a fluid?

    <p>Pressure increases linearly with depth. (C)</p> Signup and view all the answers

    What is the principle that states that pressure at a point in a fluid is the same in all directions?

    <p>Pascal's Law (A)</p> Signup and view all the answers

    Which equation is obtained from the equilibrium of forces in the x-direction for the differential element in the proof of Pascal's Law?

    <p>P<sub>1</sub> △z△y - P<sub>3</sub> △y l sinθ = 0 (B)</p> Signup and view all the answers

    A barometer is used to measure:

    <p>The atmospheric pressure. (A)</p> Signup and view all the answers

    Why is pressure considered a scalar quantity for a stationary fluid?

    <p>It only has magnitude and no specific direction. (B)</p> Signup and view all the answers

    In a connected fluid under static conditions, the pressure at the same height from the free surface is:

    <p>The same, regardless of the type of fluid. (B)</p> Signup and view all the answers

    What is the principle behind mechanical advantage, as applied in the context of hydraulic systems?

    <p>The pressure remains constant, while force is amplified by a larger area. (B)</p> Signup and view all the answers

    What is the value of 1 ban expressed in Pa?

    <p>10<sup>5</sup> Pa (C)</p> Signup and view all the answers

    In the provided example problem, why is the pressure at point 'c' greater than the pressure at point 'b'?

    <p>The pressure at point 'c' is higher due to the weight of both water and oil columns above it. (C)</p> Signup and view all the answers

    In the example problem, how is the absolute pressure at point '1' calculated?

    <p>By subtracting the sum of pressures due to each fluid column from the atmospheric pressure. (C)</p> Signup and view all the answers

    What is the principle behind the formula △P = P2 - P1 = - Pg h?

    <p>The pressure difference between two points is directly proportional to the density and the height difference. (C)</p> Signup and view all the answers

    Flashcards

    Variation of Pressure with Depth

    Describes how pressure changes with depth in a fluid due to gravity.

    Connected Fluid Pressure

    Pressure at the same height in connected fluids is equal.

    Pressure Absolute Equation

    P_abs = P_atm + pgh, relates absolute pressure to atmospheric pressure and fluid height.

    Mechanical Advantage

    The factor by which a mechanism multiplies the force put into it.

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    Barometer

    An instrument used to measure atmospheric pressure.

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    Manometers

    Devices used to measure pressure differences in fluids.

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    Layered Liquids Pressure

    Pressure in liquids changes based on the density and height of layers.

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    Pressure Calculation Example

    An example using various fluid densities and heights to find absolute pressure.

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    Pressure

    Normal force exerted by fluid per unit area.

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    Units of Pressure

    Pressure measured in Pa (N/m²), MPa, kPa, psi, and kgf/cm².

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    Absolute Pressure

    Pressure measured with reference to a vacuum.

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    Gage Pressure

    Pressure measured with reference to atmospheric pressure.

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    Pressure at a point

    Pressure is the same in all directions in a fluid.

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    Pascal's Law

    The pressure change at any point in a confined fluid is transmitted undiminished in all directions.

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    Pressure Conversion

    Conversions between different pressure units (e.g., 1 MPa = 10^6 Pa).

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    Density of liquids

    Density impacts pressure; more density leads to higher pressure at same depth.

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    Study Notes

    Pressure

    • Pressure is defined as the normal force exerted by a fluid per unit area.
    • SI unit: Pascal (Pa) = N/m². Common units include MPa and kPa.
    • USCU unit: lbf/ft² Other units include kgf/cm².
    • 1 slug = mass in USCU
    • 1 lbf = 1 lbm x 32.2 ft/s²
    • 1 lbf/in² = 1 psi
    • Conversions between units are included in the document.

    Absolute vs. Gauge Pressure

    • Absolute pressure: Pressure relative to a vacuum.
    • Gauge pressure: Pressure relative to atmospheric pressure.
    • Pabs = Pg + Patm

    Pressure at a point in a fluid

    • Pressure at a point in a stationary fluid is the same in all directions at that depth.
    • A scalar quantity for a stationary fluid

    Proof

    • The sum of forces in any direction is zero.
    • Pressure is the same at a given depth, irrespective of direction.

    Layered liquids

    • For layered liquids, pressure at a certain depth is determined by the layers above it.
    • The pressure from each layer is summed at that point.
    • Pressure increases with depth in each layer.

    Manometers

    • Manometers measure pressure differences between two points.
    • Pgas = Pabs = Patm + pgh (p = density, g = acceleration due to gravity, h = height of column).
    • A device used to measure pressure
    • Mercury or other liquids used in manometers.

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    Related Documents

    Fluid Statics Lecture 03: Pressure PDF

    Description

    This quiz covers the fundamental concepts of pressure in fluids, including definitions of absolute and gauge pressure. It explains unit conversions and the behavior of pressure at different depths in stationary fluids, as well as the impact of layered liquids. Test your understanding of these important principles in fluid mechanics.

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