PPT: Unit | General Awareness for SSC CGL PDF Download

 Page 1


Unit
Page 2


Unit
Physical Quantity and Measurement
Physical Quantity
A physical quantity is something 
we can measure, like weight, 
length, or temperature.
Measurement
T o measure something means to 
find out how much of it there is. We 
compare what we're measuring to a 
standard unit. Different systems 
use different units to measure the 
same thing.
Errors in Measurement
When we measure, we might not 
get the exact right value. There are 
three main types of errors:
Absolute Error: The difference 
between the true value and 
what we measured.
Relative Error: The absolute 
error divided by the average 
value.
Percentage Error: The relative 
error multiplied by 100.
Page 3


Unit
Physical Quantity and Measurement
Physical Quantity
A physical quantity is something 
we can measure, like weight, 
length, or temperature.
Measurement
T o measure something means to 
find out how much of it there is. We 
compare what we're measuring to a 
standard unit. Different systems 
use different units to measure the 
same thing.
Errors in Measurement
When we measure, we might not 
get the exact right value. There are 
three main types of errors:
Absolute Error: The difference 
between the true value and 
what we measured.
Relative Error: The absolute 
error divided by the average 
value.
Percentage Error: The relative 
error multiplied by 100.
System of Units
Main Systems of Units
Physical quantities are measured using four main 
systems of units:
CGS (Centimetre, Gram, Second)
FPS (Foot, Pound, Second)
MKS (Metre, Kilogram, Second)
SI (International System of Units)
Fundamental Quantities
Fundamental quantities are those that are 
independent of each other, and their units are 
called fundamental units. The most widely 
accepted system is the SI system, adopted in 1971 
by the Conference of Weights and Measures held 
in Geneva. There are seven fundamental 
quantities in the SI system, along with two 
supplementary fundamental units:
Radian (rad): Unit of plane angle.
Steradian (sr): Unit of solid angle.
Page 4


Unit
Physical Quantity and Measurement
Physical Quantity
A physical quantity is something 
we can measure, like weight, 
length, or temperature.
Measurement
T o measure something means to 
find out how much of it there is. We 
compare what we're measuring to a 
standard unit. Different systems 
use different units to measure the 
same thing.
Errors in Measurement
When we measure, we might not 
get the exact right value. There are 
three main types of errors:
Absolute Error: The difference 
between the true value and 
what we measured.
Relative Error: The absolute 
error divided by the average 
value.
Percentage Error: The relative 
error multiplied by 100.
System of Units
Main Systems of Units
Physical quantities are measured using four main 
systems of units:
CGS (Centimetre, Gram, Second)
FPS (Foot, Pound, Second)
MKS (Metre, Kilogram, Second)
SI (International System of Units)
Fundamental Quantities
Fundamental quantities are those that are 
independent of each other, and their units are 
called fundamental units. The most widely 
accepted system is the SI system, adopted in 1971 
by the Conference of Weights and Measures held 
in Geneva. There are seven fundamental 
quantities in the SI system, along with two 
supplementary fundamental units:
Radian (rad): Unit of plane angle.
Steradian (sr): Unit of solid angle.
Derived Quantities and Units of Length
Derived Quantities
Quantities obtained from fundamental 
quantities, with corresponding derived 
units. Examples: velocity, force, work, 
density, and momentum.
Unit of Length
The metre (m) is the SI unit of length, 
defined as the distance light travels in 
vacuum in 1/299,792,458 second.
Other Units of Length
Light Year: Distance light travels in 
one year (9.46 × 10¹ u m)
Parsec: Distance at which 1 AU 
subtends 1 second angle (3.085 × 
10¹ v m)
Micron (µm): 10 { v m
Astronomical Unit (AU): 1.49 × 10¹¹ 
m
Angstrom (Å): 10 {¹ p m
Nanometre (nm): 10 { y m
X-unit: 10 {¹ t m
Fermi: 10 {¹ u m
Yard: 0.9144 m
Page 5


Unit
Physical Quantity and Measurement
Physical Quantity
A physical quantity is something 
we can measure, like weight, 
length, or temperature.
Measurement
T o measure something means to 
find out how much of it there is. We 
compare what we're measuring to a 
standard unit. Different systems 
use different units to measure the 
same thing.
Errors in Measurement
When we measure, we might not 
get the exact right value. There are 
three main types of errors:
Absolute Error: The difference 
between the true value and 
what we measured.
Relative Error: The absolute 
error divided by the average 
value.
Percentage Error: The relative 
error multiplied by 100.
System of Units
Main Systems of Units
Physical quantities are measured using four main 
systems of units:
CGS (Centimetre, Gram, Second)
FPS (Foot, Pound, Second)
MKS (Metre, Kilogram, Second)
SI (International System of Units)
Fundamental Quantities
Fundamental quantities are those that are 
independent of each other, and their units are 
called fundamental units. The most widely 
accepted system is the SI system, adopted in 1971 
by the Conference of Weights and Measures held 
in Geneva. There are seven fundamental 
quantities in the SI system, along with two 
supplementary fundamental units:
Radian (rad): Unit of plane angle.
Steradian (sr): Unit of solid angle.
Derived Quantities and Units of Length
Derived Quantities
Quantities obtained from fundamental 
quantities, with corresponding derived 
units. Examples: velocity, force, work, 
density, and momentum.
Unit of Length
The metre (m) is the SI unit of length, 
defined as the distance light travels in 
vacuum in 1/299,792,458 second.
Other Units of Length
Light Year: Distance light travels in 
one year (9.46 × 10¹ u m)
Parsec: Distance at which 1 AU 
subtends 1 second angle (3.085 × 
10¹ v m)
Micron (µm): 10 { v m
Astronomical Unit (AU): 1.49 × 10¹¹ 
m
Angstrom (Å): 10 {¹ p m
Nanometre (nm): 10 { y m
X-unit: 10 {¹ t m
Fermi: 10 {¹ u m
Yard: 0.9144 m
Units of Area and Volume
Units of Area
Area relates to squared length. Key units:
Barn: 10-28 m2
Acre: 4047 m2
Hectare: 10,000 m2
Units of Volume
Volume relates to cubed length. Key units:
10 mL = 1 cL = 0.018 pint (0.021 US pint)
100 cL = 1 L = 1.76 pints
10 L = 1 daL = 2.2 gallons (2.63 US gallons)
1 cm3 = 1 mL
1 barrel = 159 L