This book follows the West Bengal Polytechnic syllabus for mechanical branch. The book is written in S I units. Notations used are as per Indian Standard Codes. Apart from West Bengal Polytechnic students of mechanical branch, it is hoped that students of other states that follow similar syllabus may also find it a useful textbook. The subject is developed systematically, using simple English and a large number of figures. At the end of each chapter a set of problems are presented along with answers so that the students can check their ability to solve problems. To enhance the ability of students to answer semester questions and examinations, a set of descriptive type, fill in the blanks type, identifying true/ false type and multiple choice questions are also given.