Physics: Units and Measurements
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Questions and Answers

Which one of the following is NOT a fundamental quantity in physics?

  • Speed (correct)
  • Length
  • Mass
  • Time

    • Derived quantities in physics can be obtained by adding or subtracting fundamental quantities.

    False (B)

    What are the three basic units in the CGS system?

    Centimeter, gram, second

    The unit of electric current is the ______.

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

    Match the fundamental quantities with their units:

    <p>Mass = Kilogram Length = Meter Time = Second Temperature = Kelvin</p> Signup and view all the answers

    Which of the following represents a derived quantity?

    <p>Area (C)</p> Signup and view all the answers

    There are ten fundamental quantities in physics.

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

    List two examples of supplementary quantities.

    <p>Plane angle, Solid angle</p> Signup and view all the answers

    What is the least count of a vernier calliper in mm?

    <p>0.1mm (A)</p> Signup and view all the answers

    A micrometer screw gauge has a main scale graduated in centimeters.

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

    What is the total reading if the main scale reading is 2.3cm and the vernier scale reading is 0.15cm?

    <p>2.45cm</p> Signup and view all the answers

    The formula for calculating the least count of a micrometer screw gauge is __ divided by the number of divisions on the thimble scale.

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

    Match the following measurements tools with their accuracy:

    <p>Vernier Calliper = ±0.1mm Micrometer Screw Gauge = ±0.01mm Main scale of Vernier Calliper = 0.01cm Vernier Scale Division = 0.01mm</p> Signup and view all the answers

    What unit of length is used in the FPS system?

    <p>Foot (C)</p> Signup and view all the answers

    The MKS system uses pound as its unit of mass.

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

    What is the name of the clocks that are the most accurate in the world?

    <p>Atomic clocks</p> Signup and view all the answers

    In the MKS system, the unit of time is the _.

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

    Match the measurement systems with their units for length:

    <p>FPS System = Foot MKS System = Meter SI System = Meter CGS System = Centimeter</p> Signup and view all the answers

    Which of the following is an application of dimensional analysis?

    <p>To check dimensional correctness of a physical relation (D)</p> Signup and view all the answers

    Weight of a body remains constant regardless of the change in gravity.

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

    What is the dimensional formula for force?

    <p>MLT^-2</p> Signup and view all the answers

    The primary purpose of a ticker tape timer is to measure both _ and _ simultaneously.

    <p>distance, time</p> Signup and view all the answers

    Which practical unit is derived from the concept of power?

    <p>Horsepower (A)</p> Signup and view all the answers

    The smallest division on a meter rule is 0.1mm.

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

    What principle does a spring balance operate on?

    <p>Hooke's law</p> Signup and view all the answers

    The dimension of velocity is expressed as _.

    <p>L/T</p> Signup and view all the answers

    What is the relationship between the main scale and the vernier scale in a vernier caliper?

    <p>The distance between two divisions differs (B)</p> Signup and view all the answers

    The SI system is a modification of the MKS system.

    <p>True (A)</p> Signup and view all the answers

    Flashcards

    What are physical quantities?

    Physical quantities are measurable aspects of the physical world, like length, mass, or time. They describe the properties of objects and events.

    What are units?

    Units are the standard measurements for physical quantities. They tell us what scale we're using, like meters for length or seconds for time.

    What are fundamental quantities?

    Fundamental quantities are independent, meaning they don't rely on other quantities for definition. Examples include length, mass, and time.

    What are derived quantities?

    Derived quantities are dependent on fundamental quantities. They are calculated using fundamental quantities. Examples include speed (length/time) and volume (length x length x length).

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    What is the CGS system?

    The CGS system is a system of units where length is measured in centimeters (cm), mass in grams (g), and time in seconds (s).

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    What is the SI system?

    The SI system is the internationally accepted system of units. It uses meters (m) for length, kilograms (kg) for mass, and seconds (s) for time.

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    What is a system of units?

    A system of units is a complete set of units, both fundamental and derived, used to measure all physical quantities. Examples include the CGS and SI systems.

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    What is a unit?

    A unit is a standard measurement for a physical quantity. For example, the unit for length could be meters, centimeters, or feet, depending on the system being used.

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    Least count of vernier caliper

    The difference between two consecutive markings on a vernier scale, used to determine the precision of the instrument.

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    Vernier caliper

    A tool used for measuring lengths with a higher precision than a ruler.

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    Vernier scale reading

    The reading on the vernier scale that coincides with a marking on the main scale, multiplied by the least count.

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    Micrometer screw gauge

    A tool specifically designed to measure very small lengths, like the thickness of a paper.

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    Least count of a micrometer screw gauge

    The smallest division that can be measured by a micrometer screw gauge.

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    FPS System

    A system using foot, pound, and second as units of length, mass, and time respectively.

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    MKS System

    Also known as the Giorgi system, this system uses meters, kilograms, and seconds for length, mass, and time.

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    SI System

    The internationally standardized system of units, based on the MKS System.

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    Mass

    The amount of matter contained in a body.

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    Weight

    The force exerted on a body due to gravity. It varies depending on the gravitational field.

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    Dimensional Formula

    A formula representing the combination of fundamental units (like Length, Mass, Time) needed to express a specific physical quantity.

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    Dimensional Analysis

    A method using dimensional formulas to check the consistency of equations or convert units.

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    Principle of Homogeneity

    The principle stating that all terms in an equation should have the same dimensions.

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    Least Count

    The smallest difference that can be measured using a measuring instrument.

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    Meter Rule

    A ruler typically graduated in centimeters and millimeters, used for measuring larger lengths.

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    Main Scale

    The main scale of a vernier caliper, graduated in centimeters and millimeters.

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    Vernier Scale

    The auxiliary scale on a vernier caliper, used for more precise measurements.

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    Reading Accuracy

    The range of possible values for a measurement, based on the least count of the instrument.

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    Study Notes

    Units and Measurements

    • Physics: A physical science studying matter, energy, and their interactions.

    Branches of Physics

    • Introduction to Physics
    • Mechanics
    • Thermal Physics
    • Electricity and Magnetism
    • Waves and Optics
    • Modern Physics

    Quantities and Units

    • Physical Quantities: Measurable parameters in physics.

    • Fundamental Quantities: Independent quantities (e.g., mass, length, time).

    • Derived Quantities: Dependent quantities, calculated from fundamental ones through multiplication or division (e.g., velocity, force). Do not subtract or add to derive these.

    • Fundamental Quantities and Units (7 generally accepted, 5 basic):

      • Mass (kilogram, kg)
      • Length (meter, m)
      • Time (second, s)
      • Thermodynamic temperature (Kelvin, K)
      • Electric current (Ampere, A)
      • Luminous intensity (Candela, cd)
      • Amount of substance (mole, mol)
      • Plane angle (radian, rad)
      • Solid angle (steradian, sr)

    • Systems of Units:

      • CGS (centimeter-gram-second)
      • FPS (foot-pound-second)
      • MKS (meter-kilogram-second)
      • SI (International System of Units): A widely used modification of MKS.

    • Practical Units: Fundamental or derived units used in specific contexts. Examples of Practical Units include a light year(distance), or horsepower (power).

    Measurement of Time

    • Time is measured using stopwatches, clocks, and ticker tape timers.
    • Accurate clocks include atomic clocks and quartz crystal clocks.
    • Sidereal time is used in astronomy.
    • Ticker tape timers measure both distance and time simultaneously.

    Measurement of Mass

    • Mass is the quantity of matter.
    • Measured using beam balances or chemical balances, which use the principle of moments.
    • Mass is constant and does not change with gravity.

    Measurement of Weight

    • Weight is the gravitational pull on an object.
    • Measured with spring balances, which operate based on Hooke's Law.
    • Weight varies with gravity.

    Dimensional Formula

    • Dimensional formula expresses a physical quantity in terms of fundamental units (M, L, T.).
    • Steps to write a dimensional formula:
      1. Write the equation for the physical quantity.
      2. Express all quantities in terms of fundamental quantities.
      3. Replace fundamental quantities with M, L, T.
      4. Indicate powers.

    Dimensional Analysis

    • Used to:
      1. Verify the dimensional correctness of an equation (principle of homogeneity)
      2. Convert units between systems (e.g., CGS to SI)
      3. Develop relationships between quantities
      4. Determine the dimensions of physical constants from equations

    Measurement Instruments

    • Meter Rule: Measures length with accuracy to 0.5 mm (0.05 cm).
    • Vernier Caliper: Measures length with higher accuracy to 0.1 mm (0.01 cm), typically used for small items like object thickness.
    • Micrometer Screw Gauge: Measures very small lengths with accuracy to 0.01 mm (0.001 cm), often used for very thin objects or small diameters.

    SI Prefixes

    • A table of SI prefixes and their values in powers of 10.

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    Description

    Explore the essential concepts of units and measurements in physics. This quiz covers various physical quantities, including fundamental and derived quantities, and the systems of units used in physics. Test your knowledge on the basic parameters that define the physical world.

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