# 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 …

## 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 …

## 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 …

## 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 …

## 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 …

## 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 …

## Atmospheric Refraction

Read – Light – Reflection and Refraction / Wonder of Light Part – II  Refraction of light rays caused due to variation in density of atmospheric air is called atmospheric refraction. Examples of Refraction in Natural Phenomenon Small – Scale Effects – (a) Mirage – on a very hot summer day in the afternoon, the …

## 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 – …

## Work and Energy – Summary

Latest CBSE syllabus topics – Work, Energy and Power – Work done by a force, energy, power. Kinetic and Potential energy, Law of conservation of energy. Latest Maharashtra SSC Board syllabus topics – Work, Energy and Power – Work done by a force, energy, power. Kinetic and Potential energy, Law of conservation of energy. Summary …

## THE MUSIC OF SOUND – Summary

Latest CBSE syllabus topics – Sound – Nature of sound and its propagation through different media, speed of sound, range of hearing in humans; ultrasound; reflection of sound; echo and SONAR Structure of the Human Ear. (Auditory aspect). Latest Maharashtra SSC Board syllabus topics – Sound – Nature of sound and its propagation through different …

## 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 …

## ELECTRIC CURRENT – Introduction and Quiz

We use the electric appliances like TV, refrigerator, electric motor, electric torch etc. Electricity is now an essential item in our life and we cannot imagine life without it.  Every month we pay for electricity by paying electricity bill. We use many terms for electricity like voltage, current, short circuit , resistance etc. We will …

## 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 …

## 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 …

## Equations of Motion by Graphical Method

When an object moves along a straight line with uniform acceleration, it is possible to relate its velocity, acceleration during motion and the distance covered by it in a certain time interval by a set of equations of motion. There are three such equations. The equations were summarized by Issac Newton. These are – Here, …

## Graphical representation of motion

[dropcap]G[/dropcap]Graphs have two axis on which two quantities can be represented and relation of the two quantities can drawn. We know that runs scored by the cricket team with overs are shown a bar graph on the television. The graphs are representation of events which can be used for comparisons etc. In mathematics, the line …

## What is Uniform and Non-uniform Motion? Give Examples.

Suppose an object moves 10 m in first 10 seconds, 10 m in second 10 seconds, 10 m in third 10seconds, then the motion of the object is uniform motion . Whereas, if the object moves different distances in same time intervals, the motion of the object is non-uniform. Suppose there are two objects A …

## Motion / Moving Objects

Introduction We see so many moving objects everyday like moving buses, trains, running cricketers, flying aeroplanes, moving ships etc. When we are sitting in a moving train, the things outside appears to be moving. When the train stops at platform, the things outside move when they are in motion. But if the another train is …