net This page intentionally left blank www.net Copyright © 2007, New Age International (P) Ltd., Publishers Published by New Age International (P) Ltd., Publishers All rights reserved. No part of this ebook may be reproduced in any form, by photostat, microfilm, xerography, or any other means, or incorporated into any information retrieval system, electronic or mechanical, without the written permission of the publisher. All inquiries should be emailed to rights@newagepublishers.com ISBN (13) : 978-81-224-2551-2 PUBLISHING FOR ONE WORLD NEW AGE INTERNATIONAL (P) LIMITED, PUBLISHERS 4835/24, Ansari Road, Daryaganj, New Delhi - 110002 Visit us at www.net Preface Mechanical Engineering being core subject of engineering and Technology, is taught to almost all branches of engineering, throughout the world. The subject covers various topics as evident from the course content, needs a compact and lucid book covering all the topics in one volume. Keeping this in view the authors have written this book, basically covering the cent percent syllabi of Mechanical Engineering (TME- 102/TME-202) of U. Technical University, Lucknow (U. From 2004–05 Session UPTU introduced the New Syllabus of Mechanical Engineering which covers Thermodynamics, Engineering Mechanics and Strength of Material. Weightage of thermodynamics is 40%, Engineering Mechanics 40% and Strength of Material 20%. Many topics of Thermodynamics and Strength of Material are deleted from the subject which were included in old syllabus but books available in the market give these useless topics, which may confuse the students. Other books cover 100% syllabus of this subject but not covers many important topics which are important from examination point of view. Keeping in mind this view this book covers 100% syllabus as well as 100% topics of respective chapters. The examination contains both theoretical and numerical problems. So in this book the reader gets matter in the form of questions and answers with concept of the chapter as well as concept for numerical solution in stepwise so they don’t refer any book for Concept and Theory. This book is written in an objective and lucid manner, focusing to the prescribed syllabi. This book will definitely help the students and practicising engineers to have the thorough understanding of the subject. In the present book most of the problems cover the Tutorial Question bank as well as Examination Questions of U. Technical University, AMIE, and other Universities have been included. Therefore, it is believed that, it will serve nicely, our nervous students with end semester examination. Critical suggestions and modifications by the students and professors will be appreciated and accorded Dr. Singh Manish Dwivedi Feature of book 1. Cover 100% syllabus of TME 101/201. Cover all the examination theory problems as well as numerical problems of thermodynamics, mechanics and strength of materials. Theory in the form of questions – Answers. Included problems from Question bank provided by UPTU. Provided chapter-wise Tutorials sheets. Included Mechanical Engineering Lab manual. No need of any other book for concept point of view.net This page intentionally left blank www.net This page intentionally left blank www.net IMPORTANT CONVERSION/FORMULA 1. Sine Rule 1 80 – β R Q 1 80 – α O 1 80 – γ α γ P P Q R = = sin (180 − α ) sin (180 − β) sin (180 − γ ) 2. Important Conversion 1N = 1 kg X 1 m/sec2 = 1000 gm X 100 cm/sec2 g = 9.5 KW 1 Pascal(Pa) = 1N/m2 1KPa = 103 N/m2 1MPa = 106 N/m2 1GPa = 109 N/m2 1 bar = 105 N/m2 3. Important Trigonometrical Formulas 1. 1 + cosA = 2cos2A/2 www.net This page intentionally left blank www.net CONTENTS Preface v Syllabus Important Conversion/Formula Part– A: Thermodynamics (40 Marks) 1. Fundamental concepts, definitions and zeroth law 1 2. First law of thermodynamics 30 3. Properties of steam and thermodynamics cycle 81 Part – B: Engineering Mechanics (40 Marks) 6. Force : Concurrent Force system 104 7. Force : Non Concurrent force system 141 8. Force : Support Reaction 166 9. Application of Friction: Belt Friction 216 11. Law of Motion 242 12. Trusses 302 Part – C: Strength of Materials (20 Marks) 14. Simple stress and strain 331 15. Compound stress and strains 393 16. Pure bending of beams 409 17. Appendix Tutorials Sheets 448 2. Previous year question papers (New syllabus) 503 www.net This page intentionally left blank www.net Fundamental Concepts, Definitions and Zeroth Law / 1 CHAPTER 1 FUNDAMENTAL CONCEPTS, DEFINITIONS AND ZEROTH LAW Q. Justify that it is the science to compute energy, exergy and entropy. (Dec–01, March, 2002, Jan–03) Sol : Thermodynamics is the science that deals with the conversion of heat into mechanical energy. It is based upon observations of common experience, which have been formulated into thermodynamic laws. These laws govern the principles of energy conversion. The applications of the thermodynamic laws and principles are found in all fields of energy technology, notably in steam and nuclear power plants, internal combustion engines, gas turbines, air conditioning, refrigeration, gas dynamics, jet propulsion, compressors, chemical process plants, and direct energy conversion devices. Generally thermodynamics contains four laws; 1. Zeroth law: deals with thermal equilibrium and establishes a concept of temperature. The First law: throws light on concept of internal energy. The Second law: indicates the limit of converting heat into work and introduces the principle of increase of entropy. Third law: defines the absolute zero of entropy. These laws are based on experimental observations and have no mathematical proof. Like all physical laws, these laws are based on logical reasoning. Thermodynamics is the study of energy, energy and entropy. The whole of heat energy cannot be converted into mechanical energy by a machine. Some portion of heat at low temperature has to be rejected to the environment. The portion of heat energy, which is not available for conversion into work, is measured by entropy. The part of heat, which is available for conversion into work, is called energy. Thus, thermodynamics is the science, which computes energy, energy and entropy. 2: State the scope of thermodynamics in thermal engineering. Sol: Thermal engineering is a very important associate branch of mechanical, chemical, metallurgical, aerospace, marine, automobile, environmental, textile engineering, energy technology, process engineering of pharmaceutical, refinery, fertilizer, organic and inorganic chemical plants. Wherever there is combustion, heating or cooling, exchange of heat for carrying out chemical reactions, conversion of heat into work for producing mechanical or electrical power; propulsion of rockets, railway engines, ships, etc., application of thermal engineering is required. Thermodynamics is the basic science of thermal engineering. 3: Discuss the applications of thermodynamics in the field of energy technology.net 2 / Problems and Solutions in Mechanical Engineering with Concept Sol: Thermodynamics has very wide applications as basis of thermal engineering. Almost all process and engineering industries, agriculture, transport, commercial and domestic activities use thermal engineering. But energy technology and power sector are fully dependent on the laws of thermodynamics. For example: (i) Central thermal power plants, captive power plants based on coal. (ii) Nuclear power plants. (iii) Gas turbine power plants. (iv) Engines for automobiles, ships, airways, spacecrafts. (v) Direct energy conversion devices: Fuel cells, thermoionic, thermoelectric engines. (vi) Air conditioning, heating, cooling, ventilation plants. (vii) Domestic, commercial and industrial lighting. (viii) Agricultural, transport and industrial machines. All the above engines and power consuming plants are designed using laws of thermodynamics. 4: Explain thermodynamic system, surrounding and universe. Differentiate among open system, closed system and an isolated system. Give two suitable examples of each system. 03) Or Define and explain a thermodynamic system. Differentiate between various types of thermodynamic systems and give examples of each of them. 2001) Or Define Thermodynamics system, surrounding and universe. (May–03) Or Define closed, open and isolated system, give one example of each. (Dec–04) Sol: In thermodynamics the system is defined as the quantity of matter or region in space upon which the attention is concentrated for the sake of analysis. These systems are also referred to as thermodynamics system. It is bounded by an arbitrary surface called boundary. The boundary may be real or imaginary, may be at rest or in motion and may change its size or shape. Everything out side the arbitrary selected boundaries of the system is called surrounding or environment.1 The system Fig.2 The real and imaginary boundaries The union of the system and surrounding is termed as universe. Universe = System + Surrounding www.net Fundamental Concepts, Definitions and Zeroth Law / 3 Types of system The analysis of thermodynamic processes includes the study of the transfer of mass and energy across the boundaries of the system. On the basis the system may be classified mainly into three parts. (1) Open system (2) Closed System (3) Isolated system (1) Open system The system which can exchange both the mass and energy (Heat and work) with its surrounding. The mass within the system may not be constant. The nature of the processes occurring in such system is flow type. Water Pump: Water enters at low level and pumped to a higher level, pump being driven by an electric motor. Heat Transfer Mass may change Mass in Boundary Mass Out free to move Work Transfer Fig.Scooter engine: Air arid petrol enter and burnt gases leave the engine. The engine delivers mechanical energy to the wheels. Boilers, turbines, heat exchangers. Fluid flow through them and heat or work is taken out or supplied to them. Most of the engineering machines and equipment are open systems. (2) Closed System The system, which can exchange energy with their surrounding but not the mass. The quantity of matter thus remains fixed. And the system is described as control mass system. The physical nature and chemical composition of the mass of the system may change. Water may evaporate into steam or steam may condense into water. A chemical reaction may occur between two or more components of the closed system. Car battery, Electric supply takes place from and to the battery but there is no material transfer. Tea kettle, Heat is supplied to the kettle but mass of water remains constant. Heat Transfer Mass may change Boundary free to move Work Transfer Fig 1. Water in a tank 4. Piston – cylinder assembly. (3) Isolated System In an Isolated system, neither energy nor masses are allowed to cross the boundary. The system has fixed mass and energy. No such system physically exists. Universe is the only example, which is perfectly isolated system.net 4 / Problems and Solutions in Mechanical Engineering with Concept Other Special System 1. Adiabatic System: A system with adiabatic walls can only exchange work and not heat with the surrounding. All adiabatic systems are thermally insulated from their surroundings. Example is Thermos flask containing a liquid. Homogeneous System: A system, which consists of a single phase, is termed as homogeneous system. For example, Mi×ture of air and water vapour, water plus nitric acid and octane plus heptanes. Hetrogeneous System: A system, which consists of two or more phase, is termed as heterogeneous system. For example, Water plus steam, Ice plus water and water plus oil. 5: Classified each of the following systems into an open or closed systems. (1) Kitchen refrigerator, (2) Ceiling fan (3) Thermometer in the mouth (4) Air compressor (5) Pressure Cooker (6) Carburetor (7) Radiator of an automobile. (1) Kitchen refrigerator: Closed system. No mass flow. Electricity is supplied to compressor motor and heat is lost to atmosphere. (2) Ceiling fan: Open system. Air flows through the fan. Electricity is supplied to the fan. (3) Thermometer in the mouth: Closed system. No mass flow. Heat is supplied from mouth to thermometer bulb. (4) Air compressor: Open system. Low pressure air enters and high pressure air leaves the compressor, electrical energy is supplied to drive the compressor motor. (5) Pressure Cooker: Closed system. There is no mass exchange (neglecting small steam leakage). Heat is supplied to the cooker. (6) Carburetor: Open system. Petrol and air enter and mi×ture of petrol and air leaves the carburetor. There is no change of energy. (7) Radiator of an automobile: Open system.
