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                                     1• INTRODUCTION We all have common sense notions of heat and temperature. Temperature is a measure of ‘hotness’ of a body. A kettle with boiling water is hotter than a box containing ice. In physics, we need to define the notion of heat, temperature, etc., more carefully. In this chapter, you will learn what heat is and how it is measured, and study the various process by which heat flows from one body to another. Along the way, you will find out why blacksmiths heat the iron ring before fitting on the rim of a wooden wheel of a horse cart and why the wind at the beach often reverses direction after the sun goes down. You will also learn what happens when water boils or freezes, and its temperature does not change during these processes even though a great deal of heat is flowing into or out of it.THERMAL PROPERTIES OF MATTER          2• TEMPERATURE AND                                 HEAT We can begin studying thermal properti

                                      1. INTRODUCTION

             1. Introduction   The motion of a body depends on how mass is   distributed within the body. We restricted ourselves to simpler situations of rigid bodies. A rigid body generally means a hard solid object having a definite shape and size. But in reality, bodies can be stretched, compressed and bent. Even the appreciably rigid steel bar can be deformed when a sufficiently large external force is applied on it. This means that solid bodies are not perfectly rigid.A solid has definite shape and size. In order to change (or deform) the shape or size of a body, a force is required. If   you stretch a helical spring by gently pulling its ends, the length of the spring increases slightly. When you leave the ends of the spring, it regains its original size and shape.  The property of a body, by virtue of which it tends to regain its   original size and shape when the applied force is removed, is known as elasticity and the deformation caused is known as elastic deforma

                    1. Introduction Any real body which we encounter in daily life has a   finite size. In dealing with the motion of extended bodies    (bodies of finite size) often the idealised model of a particle is  inadequate. In this chapter we shall try to go beyond this   inadequacy. We shall attempt to build an understanding of  the motion of extended bodies. An extended body, in the   first place, is a system of particles. We shall begin with the  consideration of motion of the system as a whole. The centre  of mass of a system of particles will be a key concept here.  We shall discuss the motion of the centre of mass of a system   of particles and usefulness of this concept in understanding  the motion of extended bodies.    A large class of problems with extended bodies can be   solved by considering them to be rigid bodies. Ideally a  rigid body is a body with a perfectly definite and  unchanging shape. The distances between all pairs of  particles of such a body do

1.Introduction The terms ‘work’, ‘energy’ and ‘power’ are frequently used in everyday language. A farmer ploughing the field, a construction worker carrying bricks, a student studying for a competitive examination, an artist painting a beautiful landscape, all are said to be working. In physics, however, the word ‘Work’ covers a definite and precise meaning. Somebody who has the capacity to work for 14-16 hours a day is said to have a large stamina or energy. We admire a long distance runner for her stamina or energy. Energy is thus our capacity to do work. In Physics too, the term ‘energy’ is related to work in this sense, but as said above the term ‘work’ itself is defined much more precisely. The word ‘power’ is used in everyday life with different shades of meaning. In karate or boxing we talk of ‘powerful’ punches. These are delivered at a great speed. This shade of meaning is close to the meaning of the word ‘power’ used in physics. We shall find that there is at b