Physics Buoyancy and Density Concepts
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Questions and Answers

Which statement is incorrect regarding buoyant force?

  • Buoyant force is equal to the weight of the liquid displaced
  • Center of buoyancy is located above the center of gravity of the displaced liquid (correct)
  • Any weight, floating or immersed in a liquid, is acted upon by a buoyant force
  • The point through which buoyant force acts, is called the center of buoyancy

    • What force lifts a body that is totally or partially immersed in a fluid?

  • Less than the weight of the body
  • The weight of the body
  • More than the weight of the body
  • Weight of the fluid displaced by the body (correct)

    • How can a relatively denser object be made to float on a less dense fluid?

  • By altering the forces acting on the object
  • By altering the shear forces acting on the object
  • By altering the shape (correct)
  • None of the mentioned

    • What condition is necessary for the stable equilibrium of a floating body?

    <p>The metacenter should lie above the center of gravity</p> Signup and view all the answers

    The metacentric height is defined as the distance between which two points?

    <p>The center of gravity and the metacenter</p> Signup and view all the answers

    What should occur for a righting couple to be formed in a floating body?

    <p>The center of gravity must be above the center of buoyancy</p> Signup and view all the answers

    Which statement correctly describes the buoyant force?

    <p>It is always directed upwards</p> Signup and view all the answers

    Which of the following best explains buoyancy?

    <p>It is the result of the pressure difference on the upper and lower surfaces of an object</p> Signup and view all the answers

    What is the effect of slow closing valves on water hammer pressure?

    <p>It considerably reduces water hammer pressure.</p> Signup and view all the answers

    Which number represents the ratio of inertia force to gravitational force?

    <p>Froude’s number</p> Signup and view all the answers

    Which geometric parameter is crucial for determining the efficiency of a channel?

    <p>Hydraulic radius</p> Signup and view all the answers

    For a channel to be economic, which parameter should be minimized?

    <p>Wetted perimeter</p> Signup and view all the answers

    What is the depth of flow in the most economical circular section to achieve maximum velocity?

    <p>0.81D</p> Signup and view all the answers

    Differential manometers are primarily used to measure what?

    <p>Difference of pressure between two points</p> Signup and view all the answers

    What condition defines non-uniform flow in a fluid?

    <p>All parameters including velocity and pressure change from point to point.</p> Signup and view all the answers

    In channel flow, which factor has the least influence on flow shape and resistance?

    <p>Flow turbulence</p> Signup and view all the answers

    Which statement is true about fluids?

    <p>Fluids always expand until they fill any container.</p> Signup and view all the answers

    What principle states that the resultant upward pressure of a fluid on a floating body is equal to the weight of the fluid displaced by the body?

    <p>Archimedes’ principle</p> Signup and view all the answers

    At what temperature is the density of water maximum?

    <p>4°C</p> Signup and view all the answers

    What is the property of a fluid that describes the attraction of its own molecules?

    <p>Cohesion</p> Signup and view all the answers

    What is the resultant upward pressure of the fluid on an immersed body commonly called?

    <p>Buoyant force</p> Signup and view all the answers

    The attraction of molecules of different kinds of fluids to each other is called what?

    <p>Adhesion</p> Signup and view all the answers

    What primarily causes the action of buoyant force on a body submerged partially or fully in fluid?

    <p>Displacement of fluid due to submerged body</p> Signup and view all the answers

    Under what condition will the normal stress in a fluid be constant in all directions at a point?

    <p>It is at rest</p> Signup and view all the answers

    What is the term for the center of gravity of the volume of the liquid displaced by an immersed body?

    <p>Center of buoyancy</p> Signup and view all the answers

    The specific weight of seawater is higher than that of pure water primarily due to the presence of what?

    <p>Dissolved salt</p> Signup and view all the answers

    What is the horizontal component of buoyant force generally regarded as?

    <p>Zero</p> Signup and view all the answers

    The contraction of a liquid's free surface to the smallest area is driven by which force?

    <p>Surface tension</p> Signup and view all the answers

    The line of action of the buoyant force acts through which of the following points?

    <p>Centroid of the displaced volume of fluid</p> Signup and view all the answers

    A liquid will wet a solid if the adhesion forces are compared to the cohesion forces are:

    <p>More</p> Signup and view all the answers

    Which statement is incorrect regarding buoyant force?

    <p>Buoyant force can only act on solid bodies</p> Signup and view all the answers

    Which of these is not a factor affecting the buoyant force on an object?

    <p>Shape of the object</p> Signup and view all the answers

    What is true about the rate of discharge in the main line compared to the discharges in the parallel pipes?

    <p>The rate of discharge in the main line is not equal to the sum of the discharges in each of the parallel pipes.</p> Signup and view all the answers

    Under what condition are two pipe systems considered equivalent?

    <p>When the head loss and discharge are the same in both systems.</p> Signup and view all the answers

    What is the term that describes the ratio of absolute viscosity to mass density?

    <p>Kinematic viscosity.</p> Signup and view all the answers

    Which factors influence the magnitude of the water hammer effect in a pipe?

    <p>Elastic properties of the pipe material.</p> Signup and view all the answers

    When does the phenomenon of water hammer occur in pipes?

    <p>When fluid is abruptly halted by closing the valve.</p> Signup and view all the answers

    How can water hammer pressure be effectively reduced?

    <p>Using slow closing valves.</p> Signup and view all the answers

    Which of the following statements about equivalent pipe systems is incorrect?

    <p>They can have different materials.</p> Signup and view all the answers

    What happens during the water hammer phenomenon?

    <p>Sudden changes in velocity result in pressure fluctuation.</p> Signup and view all the answers

    Study Notes

    Buoyancy

    • Floating objects are acted upon by the buoyant force.
    • The buoyant force is equal to the weight of the liquid displaced by the floating object.
    • The point where the buoyant force acts is known as the center of buoyancy.
    • The center of buoyancy is always located above the center of gravity of the displaced liquid.
    • According to the principle of buoyancy, a body totally or partially immersed in a fluid will be lifted up by a force equal to the weight of the fluid displaced by the body.

    Density

    • To make a denser object float on a less dense fluid, alter the shape of the object.

    Stability of Floating Bodies

    • The conditions for the stable equilibrium of a floating body are:

      • The metacenter should lie above the center of gravity.
      • The center of buoyancy and the center of gravity must lie on the same vertical line.
      • A righting couple should be formed.

    • Metacentric height is the distance between the center of gravity of the body and the metacenter.

    Water Hammer

    • Water hammer describes the pressure surge that occurs when a fluid in a pipe is suddenly stopped.
    • The magnitude of water hammer depends on:
      • The speed at which the valve is closed.
      • The length of the pipe.
      • The elastic properties of the pipe material.

    Geometric Parameter in Channels

    • The hydraulic radius determines the efficiency of a channel.
    • For a channel to be economical, the wetted perimeter should be minimized.
    • The optimum depth for maximum velocity in a circular channel is 0.81D (where D is the diameter of the channel).

    Pressure Measurement

    • A differential manometer is used to measure the difference in pressure between two points.

    Flow Regimes in Fluids

    • Non-uniform flow occurs when the velocity, depth, pressure, etc. change from point to point in the fluid flow.

    Fluids

    • A fluid cannot remain at rest under the action of any shear force.
    • The density of water is maximum at 4°C.
    • Cohesion is the property of a fluid by which its own molecules are attracted.
    • Adhesion is the property of a fluid by which molecules of different kinds of fluids are attracted to each other.
    • The normal stress in a fluid will be constant in all directions at a point only if it is at rest.
    • Specific weight of sea water is more than that of pure water because it contains dissolved salt.
    • The free surface of a liquid tends to contract to the smallest possible area due to the force of surface tension.
    • A liquid would wet the solid if the adhesion forces are greater than the cohesion forces.

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    Explore the fundamental concepts of buoyancy and density in this quiz. Understand how buoyant forces act on floating objects, the conditions for stability of floating bodies, and how to manipulate density through shape. Test your knowledge on these vital principles of fluid mechanics.

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