Physics Units and Dimensions Quiz
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Questions and Answers

Which of the following is considered a fundamental quantity?

  • Area
  • Mass (correct)
  • Speed
  • Force

    • What is the correct SI unit for measuring force?

  • Pound
  • Newton (correct)
  • Kilogram
  • Meter

    • Which of the following is not a derived quantity?

  • Temperature (correct)
  • Area
  • Volume
  • Speed

    • How is the British system of units commonly referred?

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

    Which of the following rules is correct when writing SI units?

    <p>One space is left between the numeral and the unit symbol.</p> Signup and view all the answers

    Which of the following physical quantities does not exist in the base quantities list?

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

    What is the proper way to express weight in kilograms using SI units?

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

    Which of the following is an example of a derived quantity?

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

    What occurs to a material beyond its elastic limit?

    <p>It loses its elasticity and exhibits plasticity.</p> Signup and view all the answers

    Which of the following defines ultimate strength in the context of a stress-strain curve?

    <p>The maximum ordinate value on the stress-strain curve.</p> Signup and view all the answers

    How is stress defined?

    <p>Force per unit area.</p> Signup and view all the answers

    What does strain measure in a material?

    <p>The proportionate change in length or shape.</p> Signup and view all the answers

    In terms of elastic modulus, what does a large value indicate?

    <p>Minimal deformation under applied stress.</p> Signup and view all the answers

    Which type of stress occurs when forces cause elongation of an object?

    <p>Tensile Stress.</p> Signup and view all the answers

    Why does Hooke's law not apply to all materials?

    <p>It is only applicable up to a certain stress level for elastic materials.</p> Signup and view all the answers

    What describes the behavior of a material with a small elastic modulus?

    <p>It undergoes noticeable deformation under stress.</p> Signup and view all the answers

    What does Young’s modulus (E) indicate about a material?

    <p>The ease with which it can stretch and deform.</p> Signup and view all the answers

    What happens to a ductile material when it reaches its elastic limit?

    <p>The linear stress-strain relationship is lost.</p> Signup and view all the answers

    What does the ultimate tensile strength indicate?

    <p>The maximum stress before a material breaks.</p> Signup and view all the answers

    How is Young's modulus represented mathematically?

    <p>As the gradient of the stress-strain curve.</p> Signup and view all the answers

    What does the bulk modulus (K) measure?

    <p>Resistance to uniform compression.</p> Signup and view all the answers

    What is the relationship between stress and volume in the context of the bulk modulus?

    <p>Stress is the ratio between pressure increase and volume decrease.</p> Signup and view all the answers

    What is Poisson’s ratio a measure of?

    <p>The ratio of lateral strain to longitudinal strain.</p> Signup and view all the answers

    What is a characteristic of brittle materials?

    <p>They break suddenly without much prior deformation.</p> Signup and view all the answers

    What is the formula for shear stress?

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

    Which formula represents the relationship between stress and strain?

    <p>Stress = S × strain</p> Signup and view all the answers

    If a wire's length is increased by ΔL while subjected to a force F, how is the work done expressed?

    <p>W = 1/2 F ΔL</p> Signup and view all the answers

    Which property describes the energy stored in a wire upon stretching?

    <p>Energy = stress × strain</p> Signup and view all the answers

    What is the formula for the force exerted on a bar due to temperature change?

    <p>F = Y A α ΔT</p> Signup and view all the answers

    Which of the following correctly defines shear strain?

    <p>Shear strain = x / h</p> Signup and view all the answers

    What is Young's modulus a measure of?

    <p>The material's stiffness</p> Signup and view all the answers

    In the context of a metal wire, what would happen if the wire was heated and constrained from expanding?

    <p>A tensile force would be exerted.</p> Signup and view all the answers

    What is the value of Young's modulus (Y) calculated using stress and strain for the given example?

    <p>1.84 x 10^11 N/m^2</p> Signup and view all the answers

    In the exercise with the steel wire, how much load was required to stretch the wire?

    <p>402 kg</p> Signup and view all the answers

    What is the value of the bulk modulus (B) for lead as mentioned in the examples?

    <p>7.7 x 10^9 N/m^2</p> Signup and view all the answers

    Calculate the change in volume (ΔV) of the lead sphere when the water pressure is applied.

    <p>-1.3 x 10^-3 m^3</p> Signup and view all the answers

    What is the Young's modulus calculated for the wire that stretched by 0.5 mm with an 8 kg-wt load?

    <p>1.2 x 10^11 N/m^2</p> Signup and view all the answers

    What does the energy per cubic centimeter depend on in the elongation example?

    <p>Stress and strain</p> Signup and view all the answers

    What is the resulting stress when Young's modulus and strain are known?

    <p>Stress = Y x strain</p> Signup and view all the answers

    Which of the following factors influences the wire's elongation when a load is applied?

    <p>Length and cross-sectional area</p> Signup and view all the answers

    Study Notes

    Units and Dimensions

    • Physics relies on experiments, which involve measuring physical properties like length, mass, time, etc.
    • Physical quantities can be categorized as fundamental (independent) and derived (dependent on others).
    • Fundamental quantities include:
      • Mass
      • Length
      • Time
      • Temperature
    • The International System of Units (SI) is the standard for measurement.
    • Derived quantities are derived from fundamental ones.
      • Examples: Area, Volume, Speed, Force
    • SI units are crucial for consistent and accurate measurements in science.
      • Meter (m) for length
      • Kilogram (kg) for mass
      • Second (s) for time
      • Kelvin (K) for temperature
    • There are other systems of units: CGS (centimeter, gram, second), FPS (feet, pound, second)

    Stress and Strain

    • Stress is the force applied per unit area.
    • Strain is the fractional change in length, geometry, or volume caused by stress.
    • Stress-Strain Relationship:
      • Stress = Elastic Modulus × Strain
    • The elastic modulus describes a material's resistance to deformation.
    • Hooke's Law: Relates stress and strain linearly within the elastic limit.
      • The restoring force is proportional to displacement.
    • Types of stress:
      • Tensile Stress: Stretching or pulling force
      • Compressive Stress: Force causing compression
    • Young's Modulus (E): Measures a material's resistance to stretching or compression.
      • It's the ratio of tensile stress to tensile strain.
    • Brittle Materials: Can withstand high stress but break suddenly.
    • Ductile Materials: Stretch more before breaking, have a larger elastic region.
    • Plastic Materials: Stretch significantly but aren't very strong.
    • Poisson's Ratio: Describes the change in dimensions perpendicular to the direction of stress.

    Bulk Modulus

    • Bulk Modulus (K): Measures a substance's resistance to uniform compression.
    • It's the pressure change needed to cause a given relative volume change.
    • Compressibility: The inverse of the bulk modulus.

    Shear Stress and Strain

    • Shear Stress: Force applied parallel to a surface.
    • Shear Strain: Change in the shape of an object due to shear stress.
    • Shear Modulus (S): Measures a material's resistance to shear deformation.
    • Shear Stress - Shear Strain Relationship: Stress = Shear Modulus × Strain

    Force in a Bar Due to Expansion or Contraction

    • Temperature changes can cause expansion or contraction in materials.
    • When a material is prevented from changing length, a force develops at the ends.
    • Formula for Force:
      • F = Y * A * 𝛼 * ΔT
      • Where:
        • F: Force
        • Y: Young's modulus
        • A: Cross-sectional area
        • 𝛼: Linear coefficient of expansion
        • ΔT: Change in temperature

    Energy Stored in a Wire

    • Energy stored in a stretched wire:
      • W = (1/2) * F * ΔL (Joule/erg)
      • Where:
        • W: Work done or energy stored
        • F: Force applied
        • ΔL: Change in length
    • Energy stored per unit volume:
      • Energy/Volume = (1/2) * stress * strain

    Examples

    • Example 1: Young's Modulus calculation
      • Calculate Young's modulus for a metal wire under tension.
    • Example 2: Bulk Modulus and Volume Change
      • Calculate the change in volume of a lead sphere submerged under pressure.
    • Example 3: Work Done in Stretching a Wire
      • Calculate the work done to elongate a wire and the energy stored per unit volume.

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    Units and Dimensions PDF

    Description

    Test your understanding of fundamental and derived physical quantities along with the International System of Units (SI) in this quiz. Explore concepts related to stress and strain, and their relationships in materials. Perfect for students studying introductory physics topics.

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