UNITS AND DIMENSIONS
The word dimensions are used to describe basic concepts like mass, length, time, temperature and force.Units are the means of expressing the value of the dimension quantitatively or numerically.
Example - Kilogram, Metre, Second, Kelvin, Celcius.
The four examples are the fundamental units; other derived units are
Density = mass per unit volume = kg/m3
Force = mass x acceleration = kg.m/s2 = Newton or N
Pressure = force per unit area = N/m2 =Pascal or Pa
Other unit is‘ bar’ ,
where 1 bar =1 X105 Pa =100 Kpa = 0.1 Mpa
Work = force x distance = Newton x metre = N.m==J or Joule
Power = work done per unit time= J/s = Watt or W
Term Dimension Unit
Area L*L m2
Volume L*L*L m3
Velocity L* T-1 m/s
Acceleration L*T-2 m/s2
Force M*L*T-2 N
Pressure M*L-1*T-2 N/m2 = Pa
Work M*L2*T-2 Nm = J
Power M*L2*T-3 J/s = W
Density M*L-3 kg/m3
Viscosity M*L-1*T-1 kg/ms = N s/m2
Surface Tension M*T-1 N/m
Quantity Representative symbol Dimensions
Angular velocity w t-1
Area A L2
Density r M/L3
Force F ML/t2
Kinematic viscosity n L2/t
Linear velocity V L/t
Linear acceleration A L/t2
Mass flow rate m. M/t
Power P ML2/t3
Pressure P M/Lt2
Sonic velocity C L/t
Shear stress t M/Lt2
Surface tension s M/t2
Viscosity m M/Lt
Volume V L3
Dimensions:
Dimensions of the primary quantities:
Fundamental dimension : Symbol
Length L
Mass M
Time T
Temperature T
Dimensions of derived quantities can be expressed in terms of the fundamental dimensions.
1.SYSTEM OF UNITS
1. CGS Units
2. FPS Units
3. MKS Units
4. SI Units
