Friday, 9 November 2012

Approximate value of Some Time Intervals


 Age of the Universe                         5*10 raise power 17
 Age of the Earth                               1.4*10 raise power 17
 One year                                            3.2*10 raise power 7
 One day                                             8.6*10 raise power 4
 Time between normal                        8*10 raise power -1
  Period of audible sound                    1*10 raise power -3
  Period of typical radio                       1*10 raise power -6
  Period of vibration of an                    1*10 raise power -12  
  atom in a solid   
  Period of visible light waves               2*10 raise power -15                                

Units Outside The SI

 Other units outside the SI that are currently accepted for use with the SI, subject to further review
NameSymbol   Value in SI units
nautical mile 1 nautical mile = 1852 m
knot 1 nautical mile per hour = (1852/3600) m/s
area1 a = 1 dam2 = 102 m2
hectare ha1 ha = 1 hm= 104 m2
barbar1 bar = 0.1 MPa = 100 kPa = 1000 hPa = 105 Pa
ångströmÅ1 Å = 0.1 nm = 10-10 m
barnb1 b = 100 fm2 = 10-28 m2
curieCi1 Ci = 3.7 x 1010 Bq
roentgenR1 R = 2.58 x 10-4 C/kg
radrad1 rad = 1 cGy = 10-2 Gy
remrem1 rem = 1 cSv = 10-2 Sv

Units Outside The SI

  Units outside the SI that are accepted for use with the SI
NameSymbol Value in SI units
minute (time)min1 min = 60 s
hourh1 h = 60 min = 3600 s
dayd1 d = 24 h = 86 400 s
degree (angle)°1° = ( pi/180) rad
minute (angle)'1' = (1/60)° = (pi/10 800) rad
second (angle)''1'' = (1/60)' = (pi/648 000) rad
literL1 L = 1 dm= 10-3 m3
metric ton (a)t1 t = 103 kg
neperNp1 Np = 1
bel (b)B1 B = (1/2) ln 10 Np (c)
electronvolt (d)eV1 eV = 1.602 18 x 10-19 J, approximately
unified atomic mass unit (e)u1 u = 1.660 54 x 10-27 kg, approximately
astronomical unit (f)ua1 ua = 1.495 98 x 1011 m, approximately


International System of Units

In 1960, an International committee agreed on a set of definitions and standard to describe the Physical Quantities.This System that was established is called the System International (SI).
There are to types of SI Unites which are give below by there name and symbols.

Table 1.  SI base units
SI base unit

Base quantityNameSymbol
masskilogram      kg
electric currentampereA
thermodynamic temperature      kelvinK
amount of substancemolemol
luminous intensitycandelacd


Table 2.  Examples of SI derived units

SI derived unit

Derived quantityNameSymbol
areasquare meterm2
volumecubic meterm3
speed, velocitymeter per secondm/s
accelerationmeter per second squared  m/s2
wave numberreciprocal meterm-1
mass densitykilogram per cubic meterkg/m3
specific volumecubic meter per kilogramm3/kg
current densityampere per square meterA/m2
magnetic field strength  ampere per meterA/m
amount-of-substance concentrationmole per cubic metermol/m3
luminancecandela per square metercd/m2
mass fractionkilogram per kilogram, which may be represented by the number 1kg/kg = 1

Table 3.  SI derived units with special names and symbols

SI derived unit

Derived quantityNameSymbol  Expression
in terms of
other SI units
in terms of
SI base units
plane angleradian (a)rad  -m·m-1 = 1 (b)
solid anglesteradian (a)sr (c)  -m2·m-2 = 1 (b)
frequencyhertzHz  -s-1
forcenewtonN  -m·kg·s-2
pressure, stresspascalPaN/m2m-1·kg·s-2
energy, work, quantity of heat  jouleJN·mm2·kg·s-2
power, radiant fluxwattWJ/sm2·kg·s-3
electric charge, quantity of electricitycoulombC  -s·A
electric potential difference,
electromotive force
electric resistanceohmOmegaV/Am2·kg·s-3·A-2
electric conductancesiemensSA/Vm-2·kg-1·s3·A2
magnetic fluxweberWbV·sm2·kg·s-2·A-1
magnetic flux densityteslaTWb/m2kg·s-2·A-1
Celsius temperaturedegree Celsius°C  -K
luminous fluxlumenlmcd·sr (c)m2·m-2·cd = cd
illuminanceluxlxlm/m2m2·m-4·cd = m-2·cd
activity (of a radionuclide)becquerelBq  -s-1
absorbed dose, specific energy (imparted), kermagrayGyJ/kgm2·s-2
dose equivalent (d)sievertSvJ/kgm2·s-2
catalytic activitykatalkats-1·mol

Table 4.  Examples of SI derived units whose names and symbols include SI derived units with special names and symbols
SI derived unit

Derived quantityNameSymbol
dynamic viscositypascal secondPa·s
moment of forcenewton meterN·m
surface tensionnewton per meterN/m
angular velocityradian per secondrad/s
angular accelerationradian per second squaredrad/s2
heat flux density, irradiancewatt per square meterW/m2
heat capacity, entropyjoule per kelvinJ/K
specific heat capacity, specific entropyjoule per kilogram kelvinJ/(kg·K)
specific energyjoule per kilogramJ/kg
thermal conductivitywatt per meter kelvinW/(m·K)
energy densityjoule per cubic meterJ/m3
electric field strengthvolt per meterV/m
electric charge densitycoulomb per cubic meterC/m3
electric flux densitycoulomb per square meterC/m2
permittivityfarad per meterF/m
permeabilityhenry per meterH/m
molar energyjoule per moleJ/mol
molar entropy, molar heat capacityjoule per mole kelvinJ/(mol·K)
exposure (x and gamma rays)coulomb per kilogramC/kg
absorbed dose rategray per secondGy/s
radiant intensitywatt per steradianW/sr
radiancewatt per square meter steradianW/(m2·sr)
catalytic (activity) concentrationkatal per cubic meterkat/m3

Physical Quantities

The Quantities Which Can be measured are called Physical Quantities.
The Following Quantities with Definition,Formula,Unit and Dimension are given below.
Basic MechanicalLength or Distancefundamentaldm (meter)L (Length)
Timefundamentalts (second)T (Time)
Massfundamentalmkg (kilogram)M (Mass)
Areadistance2A = d2m2L2
Volumedistance3V = d3m3L3
Densitymass / volumed = m/Vkg/m3M/L3
Velocitydistance / timev = d/tm/s
c (speed of light)
Accelerationvelocity / timea = v/tm/s2L/T2
Momentummass × velocityp = m·vkg·m/sML/T
mass × acceleration
mass × acceleration of gravity
F = m·a
W = m·g
N (newton) = kg·m/s2ML/T2
Pressure or Stressforce / areap = F/APa (pascal) = N/m2 = kg/(m·s2)M/LT2
Energy or Work
  Kinetic Energy
  Potential Energy
force × distance
mass × velocity2 / 2
mass × acceleration of gravity × height
E = F·d
KE = m·v2/2
PE = m·g·h
J (joule) = N·m = kg·m2/s2ML2/T2
Powerenergy / timeP = E/tW (watt) = J/s = kg·m2/s3ML2/T3
Impulseforce × timeI = F·tN·s = kg·m/sML/T
Actionenergy × time
momentum × distance
S = E·t
S = p·d
J·s = kg·m2/s
h (quantum of action)
Rotational MechanicalAnglefundamentalθ° (degree), rad (radian), rev
360° = 2π rad = 1 rev
Cyclesfundamentalncyc (cycles)dimensionless
Frequencycycles / timef = n/tHz (hertz) = cyc/s = 1/s1/T
Angular Velocityangle / timeω = θ/trad/s = 1/s1/T
Angular Accelerationangular velocity / timeα = ω/trad/s2 = 1/s21/T2
Moment of Inertiamass × radius2I = m·r2kg·m2ML2
Angular Momentumradius × momentum
moment of inertia × angular velocity
L = r·p
L = I·ω
J·s = kg·m2/s
ћ (quantum of angular momentum)
Torque or Momentradius × force
moment of inertia × angular acceleration
τ = r·F
τ = I·α
N·m = kg·m2/s2ML2/T2
ThermalTemperaturefundamentalT°C (celsius), K (kelvin)K (Temp.)
Heatheat energyQJ (joule) = kg·m2/s2ML2/T2
Entropyheat / temperatureS = Q/TJ/KML2/T2K
ElectromagneticElectric Charge +/-fundamentalqC (coulomb)
e (elementary charge)
Q (Charge)
Currentcharge / timei = q/tA (amp) = C/sQ/T
Voltage or Potentialenergy / chargeV = E/qV (volt) = J/CML2/QT2
Resistancevoltage / currentR = V/iΩ (ohm) = V/AML2/Q2T
Capacitancecharge / voltageC = q/VF (farad) = C/VQ2T2/ML2
Inductancevoltage / (current / time)L = V/(i/t)H (henry) = V·s/AML2/Q2
Electric Fieldvoltage / distance
force / charge
E = V/d
E = F/q
V/m = N/CML/QT2
Electric Fluxelectric field × areaΦE = E·AV·m = N·m2/CML3/QT2
Magnetic Fieldforce / (charge × velocity)B = F/(q·v)T (tesla) = Wb/m2 = N·s/(C·m)M/QT
Magnetic Fluxmagnetic field × areaΦM = B·AWb (weber) = V·s = J·s/CML2/QT

Thursday, 8 November 2012

The Branches of Physics
1.Mechanics   2.Heat & Thermodynamics  3.Electromagnetism  4.Optics  5.Sound  6.Hydrodynamics
 7.Special Relativity  8.General Relativity  9.Quantum Mechanics  10.Atomic Physics  11.Molecular Physics
12.Nuclear Physics  13.Solid State Physics  14.Particle Physics  15.Superconductivity  16.Super Fluidity
17.Plasma Physics  19.Magneto Hydrodynamics  20.Space Physics  21.Astrophysics  22.Biophysics 
23.Chemical Physics  24.Engineering Physics  25.Geo Physics