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# Tag Archives: physical quantity

## Chat Transcript with Jihin

5:45pm

the 4th dimension has always been predicted as a penalty of the reflection of light but when i searched it for long – more description has not been found ……… how can it be possible to hav a dimension which is caused to exist due to a physical matter – LIGHT !!!

The fourth dimension is time

X Y Z co ordinates are the three other

5:54pm

wow from my knowledge – its not so

5:54pm

?

5:54pm

it is said dat the fourth dimension is caused due to the penalty of reflection of light !!

for eg :

if we take a crystal cude

&

see its reflection

its not uniform

(ts our observation )

now joining the

ends of these cubes (reflection & original

give rise to the forth dimension

yup . there r diff reference

& we can only predict caz we r trapped in the 3 -d world & we cant experience dimensions superior to ud !!

5:57pm

SO, thinking like that there is no problem in arguing on multidimensions

5 or 6 or even more

If you say you have to create a theory which supports

The proposal for existence of a fourth dimension was made by mathematicians

And time was the physical quantity first accepted as the fourth dimension

5:59pm

ya who knows – it could even happen but before tat i need to study & understand a lot of concepts & i should start taking things with more observation

& need more investment ……

5:59pm

ok

The idea you were talking was developed by Mobius

## Physical Quantity

**Prabesh **wants to know more on **Physical quantities:**

Physical Quantityis a quantity which can be measured. eg; length, mass, force, time etc

(The quantities which cannot be measured are abstract. Eg; Love, anger intelligence)

## Fundamental Quantities

Gayatri Shinde asks:

“What are the 7 fundamental quantities”

Answer:

Fundamental Physical quantities are those which can be used to express (almost) all other physical quantities but the fundamental quantities cannot be expressed in terms of each other.

There are 7 Fundamentals quantities identified

- length (unit metre (m))
- mass (unit kilogram (kg))
- time (unit second (s))
- thermodynamic temperature (unit kelvin (K))
- intensity of current (unit ampere (A))
- luminous intensity (Unit candela (Cd)) and
- amount of substance (unit mole (mol))

[youtube=http://www.youtube.com/watch?v=QK6rxqJaHoo&width=480&height=390]

## Limitations of Dimensional Analysis

**Ashmeeta Bhattarai** asked:

“What are limitations of principle of homogeneity of dimensional analysis?”

**The dimensional analysis has the following limitations**

- It fails while using it to derive a relation among physical quantities, if there are more than 3 unknown variables on which a given physical quantity depends
- It does not tell whether a given Physical quantity is a scalar or a vector.
- It does not tell us the value of constants involved
- It does not always tell us the exact FORM of a relation
- It cannot be used for deriving logarithmic, trigonometric or exponential relations
- A dimensionally correct equation may not always be the correct relation. (Because there are more than one physical quantity having the same dimensions)

Know some more? Write them as comments to this post

## Principle of Homogenity of Dimensions

**Binay Sharma** asked:

“Explain the applications of the

Principle of homogenity of Dimensionsand its importance”

**Principle of homogenity of dimensions** states that “For an equation to be dimansionally correct, the dimensions of each term on LHS must be equal to the dimensions of each term on RHS.”

Applications

1. To determine the dimensions of an unknown quantity in an equation

2. To check the accuracy of an equation

3. To derive a formula connecting the given (or assumed) physical quantities

4. To convert a physical quantity from one system of unit to other