Units and Dimensions
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Transcript of Units and Dimensions
Topics-
Doing Physics
Realms of Physics
Measurement and Units
Dimensional Analysis
Significant digits
UNITS & DIMENSIONS
By N.Sridhar 1
By N.Sridhar 2
Doing Physics• Physics is the study of the fundamental laws of nature.
• These laws help us to understand the physical universe.
• Physics is also the study of the behavior and structure of matter and how matter and energy are related to each other.
• The word “physics” has originated from the Greek word ”physic” which means “nature”.
By N.Sridhar 3
The scientific inquiry has been refined through the ages and the pattern developed to find out the solutions is called the scientific method.
By N.Sridhar 4
Physics, Technology and Society
Physics is a basic, fundamental science. It is interconnected with all other natural sciences such as chemistry, and biology. We may find that many technological advances based on these sciences have roots in physical laws.
Shows the highly precise and convenient laser eye surgery which has repaired the eyesight of millions around the world.
By N.Sridhar 6
Realms of Physics• Studying “everything” is a bit of a challenge
– Divide physics into different areas of study:
By N.Sridhar 7
Fundamental and Derived Quantities
We can conveniently classify physical quantities into two categories: fundamental and derived quantities.
System of Units A complete set of units, both fundamental and derived, for all kinds of quantities is called a ‘system’ of units. (a)The FPS System. The FPS system uses foot as a unit of length, the pound as a unit of mass and the second as a unit of time.
(b) The CGS System. The CGS system uses centimetre as a unit of length, the gram as a unit of mass and the second as a unit of time.
(c) The MKS system. The MKS system is a system of units based on the metre, the kilogram and the second as the units of length, mass and time respectively.
This system was adopted by the International Electrotechnical Commission and was put into universal use on 1st January, 1940.
By N.Sridhar 8
The International System of Units; the SI UnitsThe SI is an extension and refinement of the various traditional forms of the metric system. The name SI is an abbreviation for système International d’ unites,
The SI has seven primary or fundamental units
By N.Sridhar 11
Length
Distance Length (m)Radius of Visible Universe 1 x 1026
To Andromeda Galaxy 2 x 1022
To nearest star 4 x 1016
Earth to Sun 1.5 x 1011
Radius of Earth 6.4 x 106
Sears Tower 4.5 x 102
Football Field 1.0 x 102
Tall person 2 x 100
Thickness of paper 1 x 10-4
Wavelength of blue light 4 x 10-7
Diameter of hydrogen atom 1 x 10-10
Diameter of proton 1 x 10-15
By N.Sridhar 12
MassObject Mass (kg)
visible universe ~ 1052
Milky Way galaxy 7 x 1041
Sun 2 x 1030
Earth 6 x 1024
Boeing 747 4 x 105
Car 1 x 103
Student 7 x 101
Dust particle 1 x 10-9
Bacterium 1 x 10-15
Proton 2 x 10-27
Electron 9 x 10-31
By N.Sridhar 13
TimeInterval Time (s)
Age of Universe 5 x 1017
Age of Grand Canyon 3 x
1014
Avg age of college student 6.3 x 108
One year 3.2 x 107
One hour 3.6 x 103
Light travel from Earth to Moon 1.3 x 100
One cycle of guitar A string 2 x 10-3
One cycle of FM radio wave 6 x 10-8
One cycle of visible light 1 x 10-15
Time for light to cross a proton 1 x 10-24
By N.Sridhar 14
The Multiples and Submultiples in SIWhen the SI units are either too large or too small in reference to a particular physical quantity, their multiples or submultiples in powers of ten are used. The table, given below, gives standard names of the multiples and submultiples which can be prefixed to the name of the unit concerned: