Measurement and Physical Quantities

Measurement

• Measurement is the comparison of a known quantity to an unknown one.
• Measuring is the act of determining the magnitude of a quantity.
• Examples of everyday measurements include using measuring tapes (length), stopwatches (time), and weighing scales (mass).

Physical Quantities

• Physical quantities are measurable quantities.
• They are expressed with a numerical value and a unit.

Fundamental Quantities

• Fundamental quantities cannot be expressed in terms of other physical quantities.
• Examples include mass, length, time, and temperature.

Derived Quantities

• Derived quantities can be expressed in terms of fundamental quantities.
• Examples include area, volume, density, speed, and solid angle.

Units

• A unit is a standard quantity used to compare unknown quantities.
• Units for fundamental quantities are called fundamental units (e.g., second, kilogram).
• Units for derived quantities are called derived units (e.g., square meter, cubic meter).

SI System

• The International System of Units (SI) is a system based on meter, kilogram, second, ampere, kelvin, and candela.

Fundamental Quantities: Length

• Length is the extent between two points.
• SI: meter (m).
• Light year: Distance light travels in one year (9.46 × 10¹⁵ m). Used for astronomical distances.
• Odometer: Device measuring distance.
• Parsec: A unit of distance used in astronomy (1 parsec = 3.26 light-years).
• Astronomical Unit (AU): Average distance from Earth to Sun (1.496 × 10¹¹ m).
• Fermi (f): Unit used in nuclear physics.

Fundamental Quantities: Mass

• Mass is the amount of matter in a body.
• SI: kilogram (kg).
• Atomic mass unit (amu): (1/12)th the mass of a ¹²C atom. Used for measuring subatomic particles.
• Larger weights are measured in tonnes (1 tonne = 1000 kg).

Weight

• Weight is the force of gravity acting on an object.
• Calculated as weight = mass × acceleration due to gravity.
• Weight's SI unit is newton (N).

Measuring Equipment: Mass

• Beam balance: Compares an unknown mass to a known mass.
• Electronic balance: Provides precise measurements.

Fundamental Quantities: Time

• Time is the duration of events and intervals between them.
• SI: second (s).
• Larger units: days, months, years.
• Mechanical, quartz, and atomic clocks are used for measuring time.

Fundamental Quantities: Temperature

• Temperature is a measure of hotness or coldness.
• SI: kelvin (K), also measured in Celsius (°C) and Fahrenheit (°F).
• 0 K = -273°C (absolute zero).
• Thermometers: Used for measuring temperature.

Fundamental Quantities: Electric Current

• Electric current is the flow of electric charges.
• SI: ampere (A).
• Measured with ammeters.
• Current = Charge/time.

Fundamental Quantities: Amount of Substance

• Amount of substance is the number of entities in a substance.
• SI: mole (mol).
• Mole contains 6.02 × 10²³ entities (Avogadro's number).

Fundamental Quantities: Luminous Intensity

• Luminous intensity is the power of a light source.
• SI: candela (cd).
• Measured by photometers.

Supplementary Quantities: Plane Angle

• Plane angle is the angle made by two intersecting lines.
• SI: radian (rad).

Supplementary Quantities: Solid Angle

• Solid angle is formed by planes intersecting at a point.
• SI: steradian (sr).

Derived Quantities: Area

• Area is the space occupied by a 2D shape.
• Measured in square units (e.g., m²).

Derived Quantities: Volume

• Volume is the space occupied by a 3D object.
• Measured in cubic units (e.g., m³).

Derived Quantities: Density

• Density is mass per unit volume.
• Density = mass/volume.
• SI: kg/m³.

Accuracy In Measurement

• Errors are uncertainties in measurements.
• Accuracy: Closeness to the true value.
• Precision: Closeness of repeated measurements to each other.
• Approximation: Finding a number close to the exact value.
• Rounding off: Adjusting the number of digits in a measurement.

This quiz covers the concepts of measurement, physical quantities, fundamental and derived quantities. It explores the definitions and units associated with these quantities, providing a strong foundation in understanding how measurements function in everyday life.