# STANDARD UNITS OF MEASUREMENT IN PHYSICS PDF

STANDARD UNITS OF MEASUREMENT IN PHYSICS PDF

# What is a Physics?

Physics is the study of nature and its laws. The word physics has been derived from a Greek word physis which means nature. Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy.

# Unit

The chosen standard used for measuring a physical quantity is called unit. Unit should be :

1. well defined
2. easy to reproduce
3. easy to compare
4. internationally accepted
5. independent of changes in physical conditions

# Types of Units

Units are of two types : 1. Fundamental Unit and 2. Derived Unit

Units depend on choice. Each choice of units leads to a new system (set) of units. The internationally accepted systems are 1. CGS system,2. MKS System, 3. FPS System,4. SI Units.

# Fundamental Unit

## Standard Units

Measurement of any physical quantity involves comparison with a certain basic arbitrarily chosen and widely accepted reference standard called unit.

## SI System

It is based on the following seven basic/fundamental  units and two supplementary units.

### Basic/ Fundamental Units

 Physical Quantity SI Unit Symbol Length metre m Mass kilogram kg Time second s Electric current ampere A Thermodynamic Temperature kelvin K Luminous intensity candela Cd Amount of substance mole mol

# Derived Units

 Physical Quantity cgs units SI Unit Relation Force dyne newton 1 newton = 105 dyne Work erg joule 1 joule = 107 erg

# Greatest Units

## What is light year?

It is a distance travelled by light in one year in vacuum.

 Name Measure 1 light year 9.46 × 1015 m 1 parsec 3.084 × 1016 m = 3.26 ly 1 Astronomical Unit (A.U) 1.5 × 1011 m 1 Nautical mile or Seamile 6020 ft. 1 Micron 1 µm = 10-6 m 1 Angstron (Å) 10-10 m

## Mass Units

 Name Measure 1 Metric ton 103 kg 1 Quintal 102 kg 1 Atomic Mass Unit (amu) or Dalton 1.66 × 10-27 kg 1 Slug 14.59 kg 1 Pound 0.4537 kg 1 Chandrashekhar limit 1.4 times the mass of sun = 2.8 × 1030 kg

## Time Units

 Name Mesaure 1 Solar day 86400 sec. 1 Year 365½ solar days 1 Lunar month 27.3 solar days Tropical year It is the year in which total solar eclipse occurs. Leap Year It is the year in which the month of February is of 29 days.

# Prefix Used In Metric System

 Prefix Symbol Multiplier deci d 10-1 centi c 10-2 milli m 10-3 micro µ 10-6 nano n 10-9 pico p 10-12 femto f 10-15 atto a 10-18 zepto z 10-21 yocto y 10-24 deca da 101 hecto h 102 kilo k 103 mega M 106 giga G 109 tera T 1012 peta P 1015 exa E 1018 zetta Z 1021 yotta Y 1024

If anybody have still any doubt, please comment below in box

All the best for your upcoming exam!

You can join or visit at Facebook Page or Twitter for always keep in touch with further updates.