Units and Measurements full Chapter Notes :NCERT notes ; NEET Level Notes ๐Ÿ”ฅ

NCERT based Notes of chapter Units and Measurement NEET important questions+ important questions for boards + Important formulas 

1.Introduction 

Physics is based on measurement.
To measure any physical quantity , we need:
  • A unit 
  • A measuring instrument 
Example :
  • Length - meter
  • Mass - kilogram 
  • Time - second

2. Physical Quantities 

Physical Quantities are divided into two types  :
  • Fundamental Quantities 
  • Derived Quantities
1. Fundamental Quantities: Are Independent Quantities 

SI fundamental Quantities tablele

Quantity SI Unit Symbol
Length meter m
Mass kilogram kg
Time second s
Electric current ampere A
Temperature kelvin K
Amount of substance mole mol
Luminous intensity candela cd

1. Derived Quantities

Depend on fundamental Quantities .

Example :
  • Velocity = m/s
  • Force = kg-m/s²
  • Density = kg/m³

2. SI System Of Units 

Feature of SI units
  • Internationally accepted 
  • Decimal based
  • Easy Conversion System

3. Prefix in SI System

Prefix Symbol Power
kilo k 10³
mega M 10⁶
giga G 10⁹
milli m 10⁻³
micro ฮผ 10⁻⁶
nano n 10⁻⁹

5.Measurement Of Length

  • Digram : Vernier caliper 
Instrument :
  1. Meter scale
  2. Vernier caliper 
  3. Screw gauge

๐Ÿ‘‰Least Count Formula 

Vernier caliper:

Least count = 1MSD/Number of Vernier division 

6. Measurement of Mass

Instrument :
  • Beam balance
  • Physical balance
SI unit : Kilogram (kg)

7. Measurement of Time 

Instrument:
  • Stop Watch
  • Atomic clock
SI unit : Second (s)

8. Accuracy , Precision and Errors

๐Ÿ‘‰Accuracy : How close measurement is to true value

๐Ÿ‘‰ Precision: Repeatability of measurement 

๐Ÿ’ขTypes of Error :

  • Systematic Errors
Occur due to instrument defect
  • Random Errors
Occurs Randomly
  • Gross Errors
Human mistake 

9. Significant Figures

Rules :
  • Non - Zero digits are significant 
  • Zeros between non zero digits are significant 
  • Leading zeros are not significant 
Example:
  • 0.0025 - Two significant Figures 
  • 2.050 - 4 significant Figures 

10. Rules of Significant Figures 

  • Addition / Substraction 
Answer showed have same decimal place.
  • Multiplication / Division 
Answer showed have same significant Figures 

11. Dimensions of Physical Quantities

Quantity Formula
Velocity [M⁰L¹T⁻¹]
Force [MLT⁻²]
Energy [ML²T⁻²]
Pressure [ML⁻¹T⁻²]

12. Dimensional Analysis

Uses :
  • Check correctness of equation
  • Convert units 
  • Derive formulas 

๐Ÿ‘‰ Example formula

Force :
F = ma

Dimensional formula:

[F] = [MLT-²] 

13. Important formulas

Density : p=m/v

Velocity : v=s/t

Pressure : P=f/a

Most important Topics for NEET

  1. Significant Figures 
  2. Dimensional analysis 
  3. Errors
  4. Least count
  5. SI units 
  6. Dimensions of force , pressure , energy 

NEET weightage 

  • 1-2 question every year
  • Approx 4-8 marks

Boards important Topics 

  1. Significant Figures 
  2. Errors
  3. Dimensional analysis 
  4. SI units

And if you want Important numericals and more study material related to NEET join my Telegram channel link is mentioned ๐Ÿ‘‡ 

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