Importance of Measurement

Importance of Measurement Measurement is essential to solving practical problems in dally life. To ensure compatibility, accurate measurement of physical quantities is necessary. What are physical quantitles? Physical quantities are measurable properties of objects or phenomena. Types of physical quantities Fundamental quantitles Fundamental quantities are quantities that exist independently and cannot be expressed in terms of other quantities. Examples Length metre (m) Mass kilogram (kg) Time second (s) Derived quantities Quantities that can be expressed in terms of fundamental quantities. It is calculated using fundamental quantities. Examples: Area =Length x Breadth (m²)Volume = Length x Breadth* Height (m³) Density= Mass / Volume(kg / (m ^ 3)) A physical quantity is expressed by a number Indicating its value, followed by its unit. Why do we need units? Without standardised units, measurements are Inconsistent. Standard units and the Sl system SI (International System of Units); ● Globally accepted, ● Adopted in 1960 at an International conference In Paris. ● Ensures universal consistency Advantages of Sl units: ● Standardised. ● Internationally accepted. ● Units of all other quantities can be derived from them. Units of length Sl unit: metre (m) Conversions: 1m = 100 centimetres (cm) 1cm = 10 millimetres (mm) 1m = 1000 mm 1m = 1000000 micrometres (m) Very small units: Micron (m) It is the abbreviation of micrometre. Used for measuring the thickness of plastic bags. Larger units: 1 kilometre (km) = 1000m Astronomical Unit (AU) is the average distance from the Earth to the Sun. It is approximately 150 million kilometre. Light year is the distance light travels in a year in vacuum. Light travels at a speed of approximately 300,000 km/s. Units of mass The amount of matter contained in a substance is Its mass. The unit of mass is kilogram. Its symbol is kg. SI unit: kilogram (kg) Milligram and gram are the smaller units of mass. Conversions: 1 kg = 1000 grams (g) 1 g = 1000 milligrams (mg) 1 kg = 1,000,000 mg 1 quintal = 100 kg 1 tonne = 1000 kg Units of time Si unit: second (s) Conversions 1 minute = 60 seconds 1 hour = 3600 seconds Units of volume Si unit: cubic metre (m ^ 3) Other common units 1|| tre = 1000 cubic centimetres (cm³) 1 litre = 1000 millilitres (ml) 1 litre = 1000 millilitres (ml) Density Density is mass per unit volume. Density Mass/Volume Unit kg / (m ^ 3) Derived units They are formed by combining fundamental units. Examples Area = mx m = m² Volume = m xmx m = m³ Density = kg/m³ They are the units derived from fundamental units. Rules for writing units General rules Use lowercase letters for symbols, except for those derived from names. Correct : kg, m³, N (for Newton). No plural forms in symbols Correct: 1000 kg, not 1000 kgs. Do not mix names and symbols. Correct: 1000 kg/m³ or 1000 kilogram per cubic metre. No full stop or comma after symbols. Correct: 60 cm and not 60 cm. Use a space or a dot for compound units. Correct: N·m and not Nm. Examples Incorrect: 1.5 KG Correct: 1.5 kg Incorrect: 1000 kgs/m3 Correct: 1000 kg/m³ Least count: The smallest value that can be measured using an instrument is its least count.