This book is the result of the renewed efforts of the presentTextbook Development Team with the hope that the students will appreciate thebeauty and logic of physics. The students may or may not continue to study physicsbeyond the higher secondary stage, but we feel that they will find the thoughtprocess of physics useful in any other branch they may like to pursue, be it finance,administration, social sciences, environment, engineering, technology, biology ormedicine. For those who pursue physics beyond this stage, the matter developedin these books will certainly provide a sound base.Physics is basic to the understanding of almost all the branches of science andtechnology. It is interesting to note that the ideas and concepts of physics areincreasingly being used in other branches such as economics and commerce, andbehavioural sciences too. We are conscious of the fact that some of the underlyingsimple basic physics principles are often conceptually quite intricate. In this book,we have tried to bring in a conceptual coherence. The pedagogy and the use ofeasily understandable language are at the core of our effort without sacrificing therigour of the subject. The nature of the subject of physics is such that a certainminimum use of mathematics is a must. We have tried to develop the mathematicalformulations in a logical fashion, as far as possible.