# Chapter 13 : Measurement

### Topics covered in this snack-sized chapter:

#### Measurement arrow_upward

• Measurement is the process or the result of determining the ratio of a physical quantity, such as a length, time, temperature etc., to a unit of measurement, such as meter, second or degree Celsius.
• The science of measurement is called metrology.
• Measurement is collection of quantitative data.
• A measurement is made by comparing a quantity with a standard unit.
• Physics is a mathematical science.
• The metric system is the system of measurement used by scientists to express mass, length, and volume.
• In an effort to standardize terms for the measurement of energy, force, work, and power, scientists have developed a common system of terminology called System International (SI) units

• #### Scalar and Vector arrow_upward

• Scalars are quantities that are fully described by a magnitude (or numerical value) alone.
• Examples of scalar quantities are time, volume, mass, temperature etc.
• Vectors are quantities that are fully described by both a magnitude and a direction.
• A vector of dimension n is an ordered collection of n elements, which are called components.
• Examples of vector quantities are distance, velocity, etc.
• Quantities like force, acceleration, velocity all needs to specify direction so they are vector quantities.

• #### SI units of quantities arrow_upward

• The International System of Units is the modern form of the metric system.
• It comprises a system of units of measurement devised around seven base units and the convenience of the number ten.

• ###### SI base units

• The International System of Units (SI) defines seven units of measure as a basic set from which all other SI units are derived.
• These SI base units and their physical quantities are

•  Base Quantity Name Symbol Length meter M Mass kilogram Kg Time second S Electric Current ampere A Thermodynamic Temperature kelvin K Amount of Substance mole Mole Luminous Intensity candela Cd

• ###### SI derived units

• The International System of Units (SI) specifies a set of seven base units from which all other units of measurement are formed, by products of the powers of base units. These other units are called SI derived units.

•  Derived Quantity Name Symbol Area square meter m2 Volume cubic meter m3 Speed meter per second m/s Velocity meter per second m/s Acceleration meter per second squared m/s2 Wavenumber reciprocal meter 1/M Density, Mass Density kilogram per cubic meter kg/m3 Specific Volume cubic meter per kilogram m3 /kg Current Density ampere per square meter A/m2 Energy Joule Kg m2 /s2 Force Newton Kg m/s2 Wavenumber reciprocal meter 1/M

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