- Introduction
- Rest time! Have fun
- Physics
- Chemistry
- BIOLOGY
- Reaching the age of Adolescence
- CROP PRODUCTION AND MANAGMENT
- Cells : The basic structural unit of life
- Nutrition in human beigns
- RESPIRATION IN HUMAN BEIGNS
- TRANSPORTATION IN HUMAN BEIGNS
- excretory system in human beigns
- NERVOUS SYSTEM
- PHOTOSYNTHESIS
- Respiration in plants
- REPRODUCTION IN PLANTS
- MOVEMENTS IN PLANTS
- Forest our lifeline
- WASTE WATER STORY
- WEATHER,CLIMATE AND ITS ADAPTATION .

- Reaching the age of Adolescence
- Model tests
- Animation time

## GRAVITATION

*Overview of Gravitation*

*Gravitation is the attraction between objects because of their mass. Objects can range in size from sub-atomic particles to celestial masses, such as planets, stars and galaxies. Other properties of gravitation include attraction to the center or mass, escape velocity and gravity.*

*The concept of that matter attracts other objects was formulated by Isaac Newton as the Law of Universal Gravitation. This theory has been superseded by newer theories of gravitation, such as Albert Einstein’s Theory of General Relativity and the Theory of Quantum Gravitation.*

*The Universal Gravitation Equation defines the force of attraction between two objects in ordinary situations. The equation can be simplified to give the gravity equation for objects near Earth.*

*Properties of gravitation*

*All objects consisting of matter exhibit the property of gravitational attraction and tend to move toward each other. This property is considered universal and exists throughout the Universe.*

*No shield*

*As far as we know, there is no way to shield the effect of gravitation. There are theories that there exists "dark matter" that repels standard matter, however dark matter has never been detected.*

*Center of mass*

*Between two objects, there is a center of mass of the objects. When the objects move toward each other, the will meet at the center of mass. If one is revolving around the other, as in the case of a moon around a planet, both objects are actually rotating around the center of mass.*

*Escape velocity*

*It is possible for an object to be propelled at a sufficient velocity away from another object that it will overcome the gravitational attraction between the two. An example of this is when a rocket escapes the gravitation from the Earth.*

*Gravity*

*The expressions gravity and gravitation are often commonly interchanged. However, the correct scientific terminology considers gravity as a special case of gravitation for objects near the Earth.*

*For gravitation close to other large objects, you should include the name of the object, such as: "gravity of the Moon" or "gravity of the Sun."*

*For astronomical situations, gravitation is the correct term to use.*

*Gravitational theories*

*There have been several theories trying to explain the cause of gravitation.*

*Law of Universal Gravitation*

*In 1687, Isaac Newton formulated the Law of Universal Gravitation, which states that all objects are attracted toward other objects, due to a force acting at a distance, called gravitation.*

*Theory of General Relativity*

*In 1915, Albert Einstein gave another interpretation of gravitation in his Theory of General Relativity. He stated that gravitation was the result of the curvature of space toward matter and not due to some force.*

*Verification of the theory was in explaining the unusual orbit of the planet Mercury and measuring the effect of gravitation on deflecting light waves as they pass a star.*

*Theory of Quantum Gravitation*

*Recent considerations in Quantum Physics say that gravitation is one of four fundamental forces in nature. The force of each is created by an exchange of special or virtual particles. In the case of gravitation, the particle is called the graviton. This interaction leads to an explanation of gravitation at very small distances.*

*Gravitation Equation*

*Just as there are several theories about the cause of gravitation, likewise, there are several equations that define the force.*

*Universal Gravitation Equation*

*Newton formulated the Universal Gravitation Equation, which allows the calculation of the force between two objects. The equation is:*

*F = GMm/R2*

*where*

*F is the force of attraction between two objects in newtons (N)**G is the universal gravitational constant in N-m2/kg2**M and m are the masses of the two objects in kilograms (kg)**R is the distance in meters (m) between the objects, as measured from their centers of mass*

*Gravity equation*

*The gravity equation is a simplification of the gravitational equation for objects relatively close to the Earth:*

*F = mg*

*where*

*F is the force pulling objects toward the Earth in newtons (N) or pound-force (lbs)**m is the mass of the object in kg or pound-mass**g is the acceleration due to gravity in meters per second squared (m/s2) or feet per second squared (ft/s2)*