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  Friction - Friction is a property related to two surfaces in contact, which opposes the relative motion (or tendency to slip) between them. The force responsible is called frictional force. Friction is due to: 1.Interlocking                        2.Cold welding In case of fluids we call it viscosity. 1. Interlocking: - A n interlocking is an arrangement of signal apparatus that prevents conflicting movements through an arrangement of tracks such as junctions or crossings. 2.Cold welding: - Cold welding or contact welding is a solid-state welding process in which joining takes place without fusion/heating at the interface of the two parts to be welded. Magnitude of Friction                                           F=friction force                    mue= coefficient  of friction                    N=normal force  Types of Friction 1.Kinetic Friction -When there is Relative Motion Friction always acts so as to oppose the relative motion.Simply,its a force that acts between moving su

 In the development of physics it turned out again and again how difficult, but also important it was to develop the most suitable concepts and find the relevant quantities (e.g. force or energy) in terms of which nature can be described both simply and comprehensively.Every physical quantity consists of a a measured value and a measuring unit, i.e. a pure number and a dimension. All difficulties in conversations are avoided, if we treat both parts like a product “value times dimension”. Insert: Denotations: It is an accepted thing in international physics for long time past to abbreviate as many of the physical quantities as possible by the first letter of the corresponding English word, e.g. s(space), t(time), m(mass), v(velocity), a(acceleration), F(force), E(energy), p(pressure), R(resistance), C(capacity), V(voltage), T(temperature), etc.. Of course there are some exceptions from this rule: e.g. momentum p, angular momentum l, electric current I or potential V.                  Wh

 

 In any physical phenomenon governed by several different forces, several quantities may change with time.However, some physical quantities remains constant in time.These quantities are the 'conserve quantities' of nature.This remarkable fact is the basis of many law called conservation laws. There are nearly 14 conservation laws based on symmetry principle on Physics.And from those 14 laws discussion of some of the laws are given below:   Law of conservation of linear momentum  If no external force acts on system of colliding objects, then the total momentum of the objects, in a given  direction before collision is equal to the total momentum of object in same direction after collision.      2. Law of conservation of mass energy when a body falls freely in vacuum under the effect of Earth's Gravity, the total mechanical energy (sum of kinetic and potential energy) remains constant. Both the kinetic and its potential energy change continuously with time.However the sum rema

 

                                               REFRACTION AT PLANE SURFACES Refraction is a phenomenon, due to which a ray of light deviates from its original path, while travelling from one optical medium to another optical medium. The change of direction is caused by a change in speed of light in different medium. For example, when light travels from air into water, it slows down; causing it to continue to travel at a different direction as a result it deviates. In the case of homogeneous medium light travels along a straight line. Refraction is the bending property of light as it passes from one transparent medium to another. When light passes from a less dense to more dense medium, (for example passing from air into water), the light is refracted (or bent) towards the normal as shown in [Fig. 15.1]. The bending occurs because light travels slowly in a denser medium. By the similar way, when light enters into less dense medium form high dense medium it speeds up and bends away from