Engineering Physics PH3151 Unit 1 Mechanics Notes – Centre of Mass, Rotational Dynamics & Moment of Inertia

This document contains comprehensive and clearly structured handwritten notes for Engineering Physics (PH3151) – Unit 1: Mechanics as prescribed by Anna University under the 2021 Regulation syllabus. Designed specifically for first semester engineering students, these notes provide a detailed and conceptual understanding of core mechanics topics with neatly derived formulas, step-by-step explanations, and well-labelled diagrams. Unit 1 focuses on the fundamental principles of mechanics, including systems of particles, centre of mass, rigid body dynamics, rotational motion, and moment of inertia. Each concept is explained in a logical progression, starting from basic definitions and gradually moving towards derivations and applications. The notes emphasize conceptual clarity while also covering all important mathematical derivations required for university examinations. Key topics covered in this document include: Motion of a system of particles Centre of Mass (CM) for two-particle and multi-particle systems Derivation of centre of mass coordinates Motion of centre of mass in Earth–Moon system Kinetic energy of a system of particles Translational and rotational kinetic energy Rigid body dynamics Linear motion equations Rotational motion and angular kinematics Equations of rotational motion (ω = ω₀ + αt, θ = ω₀t + ½αt², ω² = ω₀² + 2αθ) Rotational kinetic energy derivation Moment of inertia (I = Σmr²) Radius of gyration Theorems of moment of inertia Parallel Axis Theorem (with proof) Perpendicular Axis Theorem (with proof) Moment of inertia of standard bodies: Uniform rod (about centre and end) Ring Disc Rectangular lamina Hollow cylinder The notes include worked examples, formula derivations, theorem proofs, and neatly drawn diagrams that make understanding easier and revision faster. The structure closely follows the Anna University syllabus, making it highly exam-oriented and reliable for scoring well in internal and semester examinations. These notes are ideal for: First semester engineering students (all departments) Anna University students studying PH3151 Students preparing for university exams Quick revision before tests Concept clarification in Mechanics This document serves as a complete study material for Unit 1 – Mechanics, combining theory, derivations, formulas, and important concepts in one place. It is especially helpful for students who prefer handwritten explanations that simplify complex physics concepts into easy-to-understand steps. If you are looking for organized, syllabus-based, exam-focused Engineering Physics notes for PH3151 Unit 1, this document provides everything required to master Mechanics confidently.