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# Physics

## Physics-Mechanics: Points to Remember

• The study of moving objects under the action of force is called dynamics and the study of forces on bodies at rest is called statics.
• The centre of gravity of an object is a fixed point through which the entire weight of the object acts, irrespective of the position of the object.
• The acceleration due to gravity decreases with increasing altitude and it decreases with depth.
• The stability of a body is decided by the position of the centre of gravity. A body will be stable if the vertical line through the centre of gravity falls within the base.
• A projectile is defined as a body which is given an initial velocity and then allowed to move under the action of gravity.
• The Range of a projectile is the horizontal distance between the point of projection and the point where the projectile hits the ground.
• The movement of a particle in a circular path is called circular motion.
• Angular displacement of an object is measured by the angle swept by the radius at the centre as the particle moves along the circumference of a circle
• The unit of angular displacement is radian. One radian is defined as the angle subtended at the centre of the circle by an arc whose length is equal to its radius.
• Angular velocity of an object is the rate of change of angular displacement.
• Angular momentum of a particle is defined as the moment of linear momentum of the particle about the axis of rotation.
• The moment of inertia is defined as the measure of inertia of a rotating particle and is equal to the product of the mass of the particle and the square of its distance from the axis of rotation.
• The external force required to make a body move along a circular path with uniform speed and directed towards its centre is called centripetal force.
• When a body moves along a circular path, the direction of velocity changes at every point and hence it has an acceleration which is directed towards the centre. This acceleration is called centripetal acceleration.
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Last Updated on Sunday, 27 October 2013 18:33

## Working of Heat Engine

DO YOU KNOW HOW OUR CAR ENGINE WORKS???? THE ANSWER IS STATED BELOW IN DETAIL.
INTRODUCTION
Heat engine is a type of engine which convert heat energy into mechanical energy.nowadays heat engine is commonly used in any type of vehicles. there are two types of engine;
1]INTERNAL COMPULSION ENGINE
2]EXTERNAL COMPULSION ENGINE
Internal engine is a type of heat engine in which the heat energy is changed into mechanical energy in the engine itself.example-Petrol engine,Diesel engine ETC.
whereas the external engine is a type of heat engine in which heat energy is changed into mechanical
energy under thew heat engine only.Example-steam engine.
working
There is a one source in the heat engine which provides the heat to the engine which can be written as QAnd there is working substance which is engine only it works and change the heat enery into mechanical energy which is W, we all know that no engine is 100% efficient so some heat is wasted into the sink which is called as Q2 so according to the statement,
Q1=W+QOR, W=Q1-Q2
SO BY THIS WAY HEAT ENGINE WORKS IN THE VEHICLE.

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Last Updated on Friday, 17 February 2012 08:31

## What is Gravitation?

DO YOU KNOW HOW WE LIVE ON EARTH AND SEE THE STARS,SUN?

HISTORICAL INTRODUCTION:
The motion of the celestial bodies such as the Moon,The Earth,The Planets etc. has been a subject of great intrest for a long time in the ancient period.
a famous Indian astronomer and great mathematician ARYABHAT,studied these motion in great detail most likely in fifth century AD.
He found that the the Earth revolves around its own axis and moves in a circular orbit around sun and that the moon moves in a circular orbit about the earth. after thousand year of aryabhatta the brilliant combination of tycho brahe and johnaase kepler studied the planetary mition in great detail AND FIND IN THREE LAWS OF PLANETARY MOTION-

1} All planets move in elleptical orbit with the sun at a focus.
2}The radius vector from the to the planet sweeps equal area in equal time.
3}The square of the time period of a planet is proportional to the cube of the semimajor axis of the ellipse.

NEWTON'S LAW OF GRAVITATION:

FORCE IS DIRECTLY PROPOTIONAL TO THE PRODUCT OF MASSES OF TWO OBJECTS AND INVERSLY PROPOTIONAL TO THE SQUARE OF THE DISTANCE BETWEEN THEIR CENTERS.
I.E,
F IS  DIRCTLY PROP. TO M1M2
F IS INVERSLY TO 1/R
2
GRAVITATION MEANS THAT EVERY ATTARACTS EACH OTHER WITH A FORCE WHICH IS STATED ABOVE IN THE NEWTON'S LAW OF GRAVITATION.
THESE ARE THE THREE PERSONS WHO STUDIED IN DEEPLY ABOUT THE GRAVITATION.
SO THIS IS MY ARTICLE ABOUT GRAVITATION IN VERY SHORT LANGUAG.

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Last Updated on Friday, 10 February 2012 07:01

## What is CAPILLARITY?

Do you ever thought how your towel drys up the water, or why farmers are advised to plough their fields before planting, how plants absrobe water? Well it is very simple the pretty cool reason of all such events is CAPILLARITY.

CAPILLARITY:- The rise or fall of a liquid in a tube of very fine bore is know as capillarity. The tube is known as Capillary Tube.
So now you can reason out that the fabric of your towel is like a tube of very fine bore,and water rises in it . Similarly when the field is ploughed the fine pour in the soil acts as a capillary tube and helps in bringing up the moisture to the surface.