Physics Chapter on Fluids and Gases
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Questions and Answers

What characteristic differentiates a liquid from a gas in terms of compressibility?

  • Gases are incompressible while liquids have fixed volumes.
  • Liquids are regarded as incompressible, while gases can be compressed. (correct)
  • Both liquids and gases are incompressible under normal conditions.
  • Liquids can be compressed more easily than gases.

    • How does a change in volume of a gas typically occur?

  • Exclusively by gravitational forces.
  • By changes of temperature and/or pressure. (correct)
  • Only through mechanical forces applied by external agents.
  • Solely through changes in its mass.

    • What happens to a given mass of gas in the absence of a containing vessel?

  • It will have a fixed volume regardless of conditions.
  • It will dissolve into adjacent materials.
  • It will expand continuously unless restrained. (correct)
  • It will remain unchanged and static over time.

    • Which of the following best describes the nature of gases?

    <p>Gases have no fixed volume and can compress easily.</p> Signup and view all the answers

    What aspect of fluids and gases is primarily affected by pressure?

    <p>The action of pressure and buoyancy.</p> Signup and view all the answers

    What method is commonly used to achieve balance in rotating components?

    <p>Adding or removing small masses of material</p> Signup and view all the answers

    Which of the following components may need to be balanced during manufacture?

    <p>Landing-gear wheel assemblies</p> Signup and view all the answers

    What is the formula for calculating stress?

    <p>Stress = F / A</p> Signup and view all the answers

    At what point does a material begin to behave elastically according to Hooke's Law?

    <p>Below its elastic limit</p> Signup and view all the answers

    What happens if a rotating component is unbalanced at high speeds?

    <p>It leads to excessive vibration</p> Signup and view all the answers

    What is the effect of tension stress on objects?

    <p>It pulls the object apart</p> Signup and view all the answers

    Which of the following describes strain?

    <p>The change in shape from stress</p> Signup and view all the answers

    What is true regarding the relationship between stress and strain under elastic conditions?

    <p>They are directly proportional</p> Signup and view all the answers

    What happens to the center of gravity (CG) of an aircraft when passengers or baggage are moved?

    <p>It shifts due to movement.</p> Signup and view all the answers

    Why is it important to maintain the CG within a specific range?

    <p>To ensure the aircraft remains controllable.</p> Signup and view all the answers

    How does a perfectly circular disc behave when balanced around its center of gravity?

    <p>It is balanced at all positions of rotation.</p> Signup and view all the answers

    What can cause the center of gravity not to coincide with the geometric center of a rotating object?

    <p>Slight variations in thickness or dimensions.</p> Signup and view all the answers

    What effect does an unbalanced condition have on rotating components?

    <p>It causes vibration during rotation.</p> Signup and view all the answers

    What must be done to rectify an unbalanced condition in a rotating object?

    <p>Shift the center of gravity to coincide with the center of rotation.</p> Signup and view all the answers

    What defines the acceptable positions of the CG in an aircraft?

    <p>A range between a forward limit and an aft limit.</p> Signup and view all the answers

    How does uneven fuel usage from tanks in opposite wings affect the aircraft?

    <p>It can shift the aircraft's CG.</p> Signup and view all the answers

    What is the primary cause of internal stress during heat treatment of metals?

    <p>Abrupt temperature changes</p> Signup and view all the answers

    What is a potential benefit of building residual stress into materials like windscreens?

    <p>Facilitates controlled crazing during impacts</p> Signup and view all the answers

    What often initiates a fatigue failure in a moving part?

    <p>Point of highest tensile stress</p> Signup and view all the answers

    Which of the following is a factor contributing to fatigue failures?

    <p>Surface damage or stress raisers</p> Signup and view all the answers

    What is the primary function of a lever?

    <p>To perform work by lifting a load</p> Signup and view all the answers

    Why should sharp edges be avoided in mechanical parts?

    <p>They can lead to fatigue failures</p> Signup and view all the answers

    In a first-class lever, where is the fulcrum located?

    <p>Between the load and the effort</p> Signup and view all the answers

    Fatigue failures are most prevalent in which types of structures?

    <p>Metal components</p> Signup and view all the answers

    Given a first-class lever with a load of 100 kg and an effort of 10 kg, what is the mechanical advantage (MA)?

    <p>10</p> Signup and view all the answers

    How does buoyancy in liquids compare to buoyancy in gases?

    <p>The underlying theory is similar</p> Signup and view all the answers

    What does a positive mechanical advantage indicate?

    <p>The load moved is greater than the effort used</p> Signup and view all the answers

    Which of the following is an example of a second-class lever?

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

    Where are stress raisers likely to originate in a material?

    <p>Flaws formed during manufacturing</p> Signup and view all the answers

    What does the distance ratio in a lever describe?

    <p>The ratio of distances moved by each end of the lever</p> Signup and view all the answers

    How much less effort is needed in a first-class lever when the lifting arm is seven times the length of the load arm?

    <p>7 times less effort is needed</p> Signup and view all the answers

    Which of these levers would traditionally be classified as a third-class lever?

    <p>Fishing rod</p> Signup and view all the answers

    What is the mechanical advantage (MA) when using a wheelbarrow, given that the total arm length is 4 times the length of the load arm?

    <p>MA is equal to 4</p> Signup and view all the answers

    In a third-class lever, how does the load compare to the effort?

    <p>The load is less than the effort</p> Signup and view all the answers

    What type of lever is represented by an aircraft landing gear retraction mechanism?

    <p>Third-class lever</p> Signup and view all the answers

    If a system has a mechanical advantage (MA) of 4, what can we infer about the effort required compared to the load?

    <p>Effort is 4 times less than the load</p> Signup and view all the answers

    What is a significant characteristic of a third-class lever in relation to distance moved?

    <p>Moves through a greater distance than the load</p> Signup and view all the answers

    How much effort is required to lift a 200-pound load using a system where 1600 pounds of effort is applied?

    <p>The load is lifted with greater difficulty</p> Signup and view all the answers

    In the context of mechanical advantage, what does a velocity ratio represent?

    <p>The direct ratio of two speeds in the system</p> Signup and view all the answers

    Which of the following statements is true about effort and load for a wheelbarrow?

    <p>Load is applied in front of the effort</p> Signup and view all the answers

    Study Notes

    Module: B-2 Physics, Topic 2.2.1 Statics

    • Introduction:

      • Students should be able to describe forces, moments, couples, simple machines, mechanical advantage, centre-of-gravity, stress, strain, elasticity, nature and properties of solids, fluids, and gases.
      • They should also understand pressure and buoyancy in liquids (barometers).

    • Force:

      • Force is a vector quantity that causes a change in a body's state of motion.
      • Applying force can start, stop, accelerate, or decelerate a mass.

    • Vectors:

      • Vectors have both magnitude (size) and direction.
      • Scalars only have magnitude. Examples include temperature, length, and time.

    • Vector Addition:

      • To add vectors, place one vector's tail at the head of another vector, keeping the magnitudes and directions the same.
      • A resultant vector is formed from these vectors.

    • Resolution of a vector:

      • To resolve a force into components, use trigonometric ratios (sine, cosine, and tangent).

    • Resultant Force and Equilibrium:

      • Resultant force is the net force from all acting forces.
      • An object is in equilibrium when the resultant force is zero.

    • Moments:

      • Moment is the force multiplied by the perpendicular distance from the fulcrum.
      • A system is balanced when the load moment and the effort moment are equal.

    • Levers:

      • A lever is a simple machine that provides mechanical advantage to perform work.
      • Mechanical advantage (MA) is the ratio of load to effort (load/effort). A positive MA means the load is greater than the effort.
      • First-class, second-class, and third-class levers have different arrangements of fulcrum, load, and effort.

    • Velocity Ratio (VR):

      • The VR is the ratio of the distances moved by the effort and the load in a lever system.
      • It is also equal to the mechanical advantage (MA) of the system.

    • Couples:

      • A couple is a system of two equal and opposite forces that act in parallel but on different points on an object.
      • It produces a torque (rotational force or twisting force).

    • Centre of Gravity (CG):

      • The CG is the point where the whole weight of an object appears to act.
      • For regularly shaped solids with uniform density, the CG is the geometric center.
      • For irregularly shaped solids, the CG can be determined by suspending the object from different points (the intersection of the vertical lines will give the CG).

    • Balance of Rotating Objects:

      • Objects spinning will experience balanced forces around the axis.
      • The CG of an object has to coincide with the axis of rotation for balance

    • Stress, Strain, Elasticity:

      • Stress: External force per unit cross-sectional area
      • Strain: Measure of deformation resulting from stress (extension/original size * 100%)
      • Elasticity: Ability of the material to return to its original shape.
      • Stress below the elastic limit is directly proportional to strain (Hooke's Law).

    • Tension:

      • A type of stress occurring when a force pulls on an object.

    • Compression:

      • A type of stress occurring when a force pushes on an object to reduce its volume.

    • Shear:

      • A type of stress where forces act parallel to the surfaces of an object, causing layers of the object to slide over one another.

    • Torsion:

      • A type of stress resulting from twisting forces.

    • Residual Stress:

      • Internal stress in a material resulting from uneven temperature changes or manufacturing processes.
      • Can affect the component's lifespan.

    • Fatigue:

      • Failure due to repeated small loads over time.
      • Stress concentrations (sharp edges, surface damage) and flaws can initiate crack propagation.

    • Buoyancy and Pressure in Liquids:

      • Buoyancy is a force exerted on a body immersed in a fluid. It is equal to the weight of fluid displaced.
      • Pressure in liquids increases with depth.

    • Pressure in Solids:

      • Pressure in Solids is defined as Force / Area.

    • Pressure in Gases:

      • Pressure is determined by the net effect of gas molecules hitting the container walls.

    • Atmospheric Pressure:

      • Atmospheric pressure is the weight of the air column above a point.

    • Absolute and Gauge Pressure:

      • Absolute: Total pressure (relative to a vacuum)
      • Gauge: Pressure relative to atmospheric pressure

    • Differential Pressure:

      • Differences in pressure between different parts of a fluid.

    • Fluids:

      • Liquids and gases are fluids. They are substances that flow.
      • Force exerted by the fluid is perpendicular to the surface of the objects in the fluid.

    • Gases:

      • Gases have no fixed volume, but expand to occupy the volume of the container. Their pressure and volume are related by temperature.

    • Density and Specific Gravity:

      • Density is mass per unit volume.
      • Specific gravity is the ratio of the density of a substance to the density of water.

    • Refueling:

      • Specific gravity is important for determining the weight of fuel from the volume.

    • Archimedes' Principle:

      • Principle stating that a submerged body displaces a volume of fluid equal to its own volume and experiences an upward buoyant force.

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    B-2 Physics Statics Module (PDF)

    Description

    This quiz covers important concepts related to the characteristics of fluids and gases, focusing on compressibility, volume changes, and the behavior of materials under stress. It also delves into the implications of rotational balance in components and the effects of tension stress. Test your knowledge on these fundamental topics in physics!

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