Measurement of Physical Quantities

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📏 What is measurement?

Measurement= comparing the volume of an object with a standard volume

Unit= standard quantity used for measurement

🎯 Formula of measurement

Measure = Numerical Value × Unit

Example: length =5×meter= 5 meters

📊 Types of physical quantities

Type	Explanation	example	Memoir
Basic sizes (Fundamental Quantities)	which are independent of other quantities stand alone	Length, Mass, Period, Temperature, Current, Luminosity, Volume of matter	🎯7 basic sizes
Route sizes (Derived Quantities)	Dependent on basic quantities A combination of two or more	Area, Volume, Velocity, Acceleration, Force, Work	🎯Based on

🔢 7 base quantities - SI units

No	Base size	SI unit	code	Memory Trick
1	Length	meter	m	"L = Length = Meter"
2	Mass	Kilogram	kg	"M = Mass = Kilogram"
3	Time	second	s	"T = Time = Second"
4	Temperature	Kelvin	K	"Temp = Kelvin"
5	Electric Current	Ampere	A	"Current = Ampere"
6	Luminous Intensity	Candila	cd	"Light = Candela"
7	Amount of Substance	Mole	mol	"Substance = Mole"

🎯 TNPSC Shortcut - "LMT TALS"

L- Length (Length) - m
M- Mass (Mass) - kg
T- Time (period) - s
T- Temperature (Temperature) - K
A- Ampere/Current - A
L- Luminous Intensity - cd
S- Substance Amount - mol

📝 Important questions

Q:What are the base quantities in SI system?
A:7 ✅

Q:What is the SI unit of mass?
A:Kilogram (kg) ✅

Q:What is the SI unit of temperature?
A:Kelvin (K) ✅ (Not Celsius!)

📐 Systems of Units

📊 Comparison of major unit methods

Unit method	length	Mass	Period	application
CGS method (Centimeter-Gram-Second)	Centimeter (cm)	gram (g)	Second (s)	Laboratories, small scales
MKS method (Meter-Kilogram-Second)	meter (m)	Kilogram (kg)	Second (s)	Common usage
FPS mode (Foot-Pound-Second)	feet (ft)	pound (lb)	Second (s)	Britain, America
SI method (International System)	meter (m)	Kilogram (kg)	Second (s)	🌟 Globally accepted

🌟 SI System (Système International)

Important information about the SI system

Introduction	1960- France
CGPM	General Conference on Weights and Measures
Basic units	7
Sub-units	2(radian, steradian)
Accepted countries	Most countries of the world

📐 SI Supplementary Units (Supplementary Units)

Size	unit	code	Explanation
Plane Angle	Radian	rad	An arc equal to the radius of the circle
Solid Angle	Steadiene	sr	3D angle of the sphere

🔄 Unit conversions - important

Change	value	Memory Trick
1 kilometer	1000 meters	"kg = 1000"
1 meter	100 cm	"Centi = 100th"
1 meter	1000 millimeters	"Milli = one part in 1000"
1 kilogram	1000 grams	"kg = 1000"
1 hour	3600 seconds	"60 × 60 = 3600"
1 day	86400 seconds	"24×3600"
1 light year	9.46 × 10¹² km	"Distance of light in 1 year"

📏 Prefixes

prefix	code	value	example
Tera	T	10¹²	1 TB = 10¹² bytes
Giga	G	10⁹	1 GB = 10⁹ bytes
Mega	M	10⁶	1 MHz = 10⁶ Hz
Kilo	k	10³	1 km = 10³ m
Centi	c	10⁻²	1 cm = 10⁻² m
Milli	m	10⁻³	1 mm = 10⁻³ m
Micro	μ	10⁻⁶	1 μm = 10⁻⁶ m
Nano	n	10⁻⁹	1 nm = 10⁻⁹ m

🎯 Shortcut - "TGMK cmμn"

Major:T(12) → G(9) → M(6) → K(3)
Small ones:c(-2) → m(-3) → μ(-6) → n(-9)

🔬 Derived Quantities

Route sizes= Quantities obtained by adding or dividing base quantities

📊 Main way quantities - formula & units

route size	formula	SI unit	CGS unit	Memory Trick
Area	Length × Width	m²	cm²	"L × L = L²"
Volume	Length × Width × Height	m³	cm³	"L × L × L = L³"
Density	Mass / Volume	kg/m³	g/cm³	"ρ = M/V"
Speed	Distance / Duration	m/s	cm/s	"v = d/t"
Velocity	Displacement / Period	m/s	cm/s	"Direction + Speed"
Acceleration	Change in velocity / period	m/s²	cm/s²	"a = Δv/t"
Force	Mass × Acceleration	Newton (N)	dyne	"F = ma"
Work	force × distance	Joule (J)	erg	"W = F × d"
Energy	Ability to work	Joule (J)	erg	"E = Work Unit"
Power	Job / Period	Watt (W)	erg/s	"P = W/t"
Pressure	force / area	Pascal (Pa)	dyne/cm²	"P = F/A"

🎖️ SI units with special names

Size	SI unit	code	whose name	equal to
key	Newton	N	Isaac Newton	kg·m/s²
Work, energy	Joule	J	James Zool	N·m = kg·m²/s²
ability	Watt	W	James Watt	J/s
Pressure	Pascal	Pa	Blaise Pascal	N/m²
frequency	Hertz	Hz	Heinrich Hertz	1/s
voltage	Volt	V	Alessandro Volta	W/A
electrical resistance	Omg	Ω	George Ohm	V/A
Condensation	Farat	F	Michael Faraday	C/V
magnetic field	Tesla	T	Nikola Tesla	Wb/m²

🔄 CGS & SI conversions

Size	Change	remember
key	1 N = 10⁵ dyne	"5 zeroes"
Work	1 J = 10⁷ erg	"7 zeros"
ability	1 W = 10⁷ erg/s	"7 zeros"
Pressure	1 Pa = 10 dyne/cm²	"1 zero"

🎯 Shortcut - "5-7-7-1"

Key:10⁵ (5 zeros)
Job:10⁷ (7 zeros)
Capacity:10⁷ (7 zeros)
Pressure:10¹ (1 zero)

🔧 Measuring Instruments

📏 Length measurement tools

Tool	Measuring range	The smallest size	application
Meter scale	up to 1 m	1 mm	Common length measurement
Vernier scale (Vernier Caliper)	Up to 15 cm	0.01 cm = 0.1 mm	Inner, outer diameter, depth
Screw gauge (Screw Gauge)	up to 2.5 cm	0.001 cm = 0.01 mm	Wire, plate thickness
Spherometer (Spherometer)	-	0.001 cm	Bend radius, glass thickness

🎯 Vernier vs Screw Gauge - Comparison

Detail	Vernier scale	Screw gauge
Least Quantity (LC)	0.01 cm	0.001 cm
Accuracy	less	more (10 times)
Inventor	Pierre Vernier (1631)	William Gascoigne (1638)
to measure	Inner, outer diameter, depth	Smaller thicknesses

⚖️ Mass Measuring Instruments

Tool	Type	application
Legal balance	Mechanical	Laboratory, Jewellery
Electronic scale	Electronic	Accurate measurement
Body weight scale	Spring	body weight
Plate scale	Mechanical	Vegetables, fruits

⏱️ Time measurement tools

Tool	Accuracy	application
Sundial	min	ancient times
Sand clock	min	specified time
Pendulum clock	second	houses
Quartz watch	Milli second	Wrist watch
Atomic clock	10⁻⁹ second	🌟 Very accurate
Stopwatch	0.01 second	game

🌡️ Temperature measuring instruments

Thermometer	limit	application
Medical thermometer	35°C - 42°C	Body temperature
Laboratory thermometer	-10°C - 110°C	Laboratory
Maximum-Minimum	-	Weather
Digital thermometer	-	Accurate measurement

📝 Important questions

Q:Smallest scale of vernier scale?
A:0.01 cm (0.1 mm) ✅

Q:Smallest size of screw gauge?
A:0.001 cm (0.01 mm) ✅

Q:Which is the most accurate watch?
A:Atomic clock

🎯 Measurement - Master Shortcut Chart

📊 7 Basic Sizes - Quick Reference

Size	SI unit	code	Memory Trick
length	meter	m	Length = Meter
Mass	Kilogram	kg	Mass = Kilogram
Period	second	s	Time = Second
temperature	Kelvin	K	🔴 Kelvin (NOT °C)
current	Ampere	A	Ampere
Transmittance	Candila	cd	Candela = Candle
Size of item	Mole	mol	Mole

🏆 Special Units - Scientists name

unit	Size	Scientist
Newton	key	Isaac Newton
Joule	Work, energy	James Zool
Watt	ability	James Watt
Pascal	Pressure	Blaise Pascal
Hertz	frequency	Heinrich Hertz
Volt	voltage	Alessandro Volta
Omg	electrical resistance	George Ohm
Farat	Condensation	Michael Faraday
Tesla	magnetic field	Nikola Tesla
Cooloom	Charge	Charles Coolum

🔢 Memorize important numbers

Detail	value	Trick
SI base units	7	"7 Fundamentals"
SI sub-units	2	"rad, sr"
SI Introductory Year	1960	"Sixty = 60"
Vernier LC	0.01 cm	"2 decimals"
Screw gauge LC	0.001 cm	"3 decimals"
1 N = ? dyne	10⁵	"5 zeroes"
1 J = ? erg	10⁷	"7 zeros"

📝 Frequently asked MCQ

1.What are the base units in SI system?
a) 5 b) 6c) 7 ✅d) 8

2.SI unit of temperature?
a) Celsius b) Fahrenheitc) Kelvin ✅d) Rankin

3.SI unit of force?
a) Dineb) Newton ✅c) Erg d) Joule

4.1 newton = how many dynes?
a) 10³ b) 10⁴c) 10⁵ ✅d) 10⁶

5.Smallest scale of vernier scale?
a) 0.1 cmb) 0.01 cm ✅c) 0.001 cm d) 1 mm

6.Smallest size of screw gauge?
a) 0.1 cm b) 0.01 cmc) 0.001 cm ✅d) 0.1 mm

7.SI unit of capacity?
a) Jouleb) Watt ✅c) Newton d) Pascal

8.SI unit of pressure?
a) N/mb) Pascal (N/m²) ✅c) Joule d) Watt

9.The most accurate watch?
a) Quartz b) Pendulumc) Atomic clock ✅d) Digital

10.In which year SI system was introduced?
a) 1950b) 1960 ✅c) 1970 d) 1980

🎯 Final Memory Trick - "UNITS"

U- Units are 7 fundamental + 2 supplementary
N- Newton for Force (10⁵ dyne)
I- International System = SI (1960)
T- Temperature in Kelvin (NOT Celsius!)
S- Screw gauge more accurate than Vernier

⚠️ Common Mistakes - Things to Avoid

❌ Temperature SI unit Celsius → ✅Kelvin (K)

❌ The SI unit of mass is gram → ✅Kilogram (kg)

❌ CGS unit of force is Newton → ✅ NewtonSI, Dine CGS

❌ Vernier precision → ✅Screw gaugeVery accurate

❌ 1 N = 10⁷ dyne → ✅1 N = 10⁵ dyne

📐 formula summary

Speed	v = d/t	m/s
Acceleration	a = Δv/t	m/s²
key	F = ma	N (kg·m/s²)
Work	W = F × d	J (N·m)
ability	P = W/t	W (J/s)
Pressure	P = F/A	Pa (N/m²)
density	ρ = m/V	kg/m³

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