Units and Measurements NEET Notes – Detailed Guide

Importance of Units and Measurements in NEET

Units and Measurements is one of the foundational chapters in Physics. It introduces students to the concept of physical quantities, their units, and the systems of measurement. Mastery of this chapter is essential as it is frequently linked to numerical and conceptual questions in NEET. It builds the base for advanced chapters like Mechanics, Thermodynamics, and Electrodynamics.

Physical Quantities and Their Classifications

Physical quantities refer to properties of objects that can be measured. These are broadly classified into:

• Fundamental Quantities: These are basic quantities that cannot be derived from other quantities. Examples include:

  • Length

  • Mass

  • Time

  • Temperature

  • Electric Current

  • Amount of Substance

  • Luminous Intensity

• Derived Quantities: These are quantities derived from fundamental ones through mathematical relationships. Examples include:

  • Speed

  • Acceleration

  • Force

  • Pressure

  • Energy

SI Units and System of Measurements

The International System of Units (SI) is the most widely accepted measurement system used in science and engineering.

Seven Fundamental SI Units:

Additionally, we have supplementary and derived units like:

• Newton (N) for force

• Joule (J) for energy

• Pascal (Pa) for pressure

• Coulomb (C) for charge

Measurement Errors and Their Types

Measurement error is the difference between the measured value and the true value. These errors arise due to limitations in instruments, human mistakes, or environmental factors.

Types of Measurement Errors:

• Systematic Errors: Consistent and predictable; due to instrument calibration, environmental changes, or observer bias.

• Random Errors: Irregular errors due to unpredictable fluctuations.

• Gross Errors: Due to human negligence or instrument failure.

• Absolute Error: Difference between measured and actual value.

• Relative Error: Ratio of absolute error to actual value.

• Percentage Error: Relative error expressed in percentage.

Significant Figures and Rounding Off

Significant figures indicate the precision of a measurement. The number of significant figures depends on the accuracy of the measuring instrument.

Rules for Significant Figures:

• All non-zero digits are significant.

• Zeros between non-zero digits are significant.

• Trailing zeros after the decimal point are significant.

• Leading zeros are not significant.

Operations with Significant Figures:

• In addition/subtraction, result is reported to the least number of decimal places.

• In multiplication/division, result is reported to the least number of significant figures.

Rounding off ensures that numbers reflect the correct degree of accuracy without misleading precision.

Dimensional Analysis and Its Applications

Dimensional analysis is a technique used to verify equations, convert units, and derive physical relations using dimensions of quantities.

Applications:

• Checking dimensional consistency of equations (Principle of Homogeneity).

• Unit conversions across systems (e.g., from CGS to SI).

• Deriving formulas using the dimensional method.

Example:

• Formula for force:
  F = ma
  Dimensions = [M¹L¹T⁻²]

Key Formulas from Units and Measurements for NEET

Here are some important formulas frequently used in NEET:

• Speed = Distance / Time

• Acceleration = Velocity / Time

• Force = Mass × Acceleration

• Work = Force × Displacement

• Density = Mass / Volume

These formulas are essential for solving numerical problems accurately and quickly in NEET Physics.

Why Study Units and Measurements for NEET?

• Forms the foundation for all other physics topics.

• Helps in solving numerical questions involving units, conversion, and error analysis.

• Frequently appears in both direct and application-based questions in NEET.

• Boosts concept clarity for dimensional analysis, which is useful in derivations and theoretical questions.

Download Free NEET Notes – Units and Measurements

Get access to concise, high-quality notes specially curated for NEET aspirants. These notes help in quick revision before exams and ensure strong concept-building. PDF download options are available to allow offline study anytime, anywhere.