Units and Dimensions

PHYSICS :-
the study about nature and happens events in whole universe is called physics

PHYSICAL QUANTITIES

The term quantities in physics is describe the laws of physics ,
Basically , there are two types of physical quantities

1. Fundamental quantities

2. Derived quantities

Fundamental quantities :-

The physical quantities which are do not depend each other , and can't be further resolved into any other physical quantities are known as fundamental quantities .

There are seven fundamental physical quantities .

Fundamental units symbol

Quantities

(a) length metre m

(b) mass kilograms kg

(c) time second sec

(d) current Ampere A

(e) temperature kelvin k

(f) luminous

intensity candela cd

(g) Amount of

Substance Mole mol.

Derived quantities :-

The physical quantities which depends on the fundamental quantities , in other way we can say that , the physical quantities which can derived from fundamental quantities.

For example -

Speed = Distance/time

Density = mass/volume

UNITS

The term of physics that which measured quantaty , are known as unit .

physical quantity = magnitude × unit

There are three types of units

Fundamental units
Derived units
Supplementary units

Fundamental units :-

The units of fundamental quantities are called fundamental units

Metre , kilograms , second , Ampere , Kelvin , candela , mole

Properties of fundamental units :-

(i) they are well defined

(ii) they are easily reproducible at all places

(iii) they do not vary with temperature, time
pressure etc. i.e. invariable.

(iv) there are seven fundamental units.

Derived units:-

The units of derived quantities are called derived units , for example -

Volume = ( lenght )³ = m³

Supplementary units :-

The units defined for the supplementary quantities, namely plane angle and solid angle are called the supplementary units.

The unit for plane angle is radian and the unit for the solid angle is steradian

NOTE " - The supplemental quantities have only units but no Dimensions.

MEASUREMENT SYSTEM OF UNITS

Generally units are measured in three systems,

M.k.s. units system (metre : kilogram : second )

C.g.s. units system (centimeter : gram : second )

F.p.s. units system ( foot : pound : second )

And , Another international system of units measurements are SI system

System of international (SI)

In , year of 1971 international bureau of units measurements held it's meeting and decided system of units , which is known as the international system of units .

DIMENSIONS

The power to which the fundamental quantities must be rise to present the given physics quantities is called Dimensions of physical quantities .

Force = mass × acceleration

→ mass × velocity /time

∴ velocity = acceleration/time

→ mass × ( length )/ (time)²

So Dimensions of force = 1 in mass

= 1 in length

= - 2 in length

And , Dimensions formula = [ M L T- 2 ]