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Physics

Property of Sound Waves that Sound needs Material Medium to Travel

The sound waves need material medium to travel because they travel by the vibrations of particles of the medium. The material medium is gas, liquid and solid.  Sound waves are called mechanical waves as they need a material medium for their travel.  An activity described below tells that sound can not travel through vacuum. The …

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Work, Energy, Power – Question and solution

A body of mass 20 kg is projected vertically upwards with a velocity of 20m/s. Find – (a) its potential energy at the starting point         (b) its kinetic energy at the starting point         (c) its potential energy at the highest point          (d) its kinetic energy at the highest point. Answer – (a) its potential energy …

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Force and Laws of Motion – Balanced and Unbalanced Force, Inertia, Types of Inertia   

When the sum of forces becomes zero, the forces balance each-other and the forces are called balanced forces. Activity – We take a box and tie two strings to it in opposite direction. One string is at end A and other string is at end B. When we pull string at A, the box moves …

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FORCE AND LAWS OF MOTION / THE LAWS OF MOTION – SUMMARY

Summary – If the resultant of all the forces acting on a body is zero, the forces are called balanced forces. If the resultant of all the forces acting on a body is not zero, the forces are called unbalanced forces. An unbalanced force acting on a body gives it an acceleration. Force is an …

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Electric Symbols and Electrical Circuits – Introduction and Quiz

Read First – Electric Current Circuit is a continuous path consisting of conducting wires and other resistances between the terminals. Electric circuit is a continuous path made by conducting wires, devices such as resistances, capacitors etc. and voltage sources. A continuous / closed path consisting of conducting wires and other resistances between the terminals of a …

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Defects of Eyes and their Remedies     

Read – Human Eye and Colorful World  -Eye -Structure Some people can not see clearly objects due to loss of power of accommodation of eye. Such problem may be due to – 1. weakening of ciliary muscles                                                                                                          2. change in size of eyeball                                                                                                     3. Irregularity on the surface of cornea                                                                                               4. Formation of membrane …

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Gravitation – Summary

Latest CBSE syllabus topics – Gravitation – Gravitation, universal law of gravitation, force of gravitation of the earth (earth’s gravity), acceleration due to gravity, mass and weight, free fall. Flotation – Thrust and Pressure, Archimedes’ Principle, Buoyancy, Elementary idea of relative density. Latest Maharashtra SSC Board syllabus topics – The Pull of the Earth – …

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Magnetic Effects of Electric Current -To see the effect of magnetism of bar magnet on iron fillings

Magnets are fancy of children. So many toys use magnets. However magnets have many applications. Magnet attracts iron, nickel and cobalt objects , the unlike poles of magnets attract each other however the like poles of magnets repel each other. Magnets are natural magnets (permanent magnets) and man-made magnets. Earth as magnet – A freely …

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HUMAN EYE AND COLOURFUL WORLD / WONDERS OF LIGHT PART – I

Eye is the most important sense organ. It is the sense organ through which we can see the world and we can watch the different colours. Eye is similar to camera in the sense that the light enters through cornea and image is formed on a light sensitive screen called retina inside the eye. There …

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Light – Refraction of Light

Refraction is the bending (change in the direction) of a wave (light or sound). When a light ray passes from one transparent medium to another, it changes speed and bends. Example : Light traveling from air and going into water – half submerged straight stick or pencil into water.                        The stick appears bent …

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