GRAVITY

GRAVITY N GRAVITATION:

• Gravity and Gravitation are totally different.

• Gravity is mainly 1 of the most important phenomenon in earth.Gravity is denoted by small letter 'g',If any person or object should move away from earth he need to cross the gravitational force g=9.8 metres/seconds square.

• Rocket is the only source for human to travel against gravity from the earth to other planets n natural satellites(moon).

• Gravity's exact meaning is explained by Sir Isaac Newton.Newton has proposed Three Laws Of Motion..In these Newtons Third Law is important according to it

• Every Action has an Equal an Opposite Reaction.

• Example:N1 is the force acting on the system then according to Newtons Third Law-->>                                                                  +N1(plus N1) = -N1(minus N1)

•  Rocket follows the principle Newtons Third Law Of Motion.

• Gravity is the attraction of every body to every other body due to the masses of each body. The larger the mass, the greater the force. It also depends on the distances: the closer the bodies, the greater the force. Gravity is directed toward the center of a body, and the distance is measured from the center. Gravity keeps the moon going around the Earth, the Earth going around the Sun, and the Sun going around the center of the Milky Way. Gravity is the weakest of the four fundamental forces of nature (electromagnetic, weak nuclear, and strong nuclear are the other three), yet it is the force that governs motion in the universe.

The force of gravity (F) depends on the masses of the two bodies (m₁, m₂) and the distance between the bodies' centers (r). There is a direct proportion between mass and gravitational force: If you double the mass of one body, the gravitational force between them is also doubled. The gravitational force is inversely proportional to the square of the distance
                                                          F = G(m₁m₂)/r^{2where                                          G = 6.67 x 10-11 Nm2/kg2                                                                   here G is called} universal gravitational constant equal and people gets confused from "G" and "g"...............g is called force due to gravity and its value differs from the earths surface to moon surface.....the value of g will change as an object is moved further from Earth's center.....Although the symbol g is sometimes used for standard gravity, g (without a suffix) can also mean the local acceleration due to local gravity and centrifugal acceleration, which varies depending on one's position on Earth.....
                                             
                                                     g(on earth)= 9.8 m/s²        

ASTRONOMY BASICS

UNIVERSE :

The universe is simply denoted by U.The Universe consists of galaxies.            

     ASTRONOMY:

The Study of Celestial Objects in Universe like Stars,Planets and all is known as Astronomy.It is built on Greek root astron = star and nomos = arrangement, order or law. Astronomy, therefore, is the study of arrangement of stars. It is the branch of Physics that studies celestial bodies and the Universe as a whole. ORIGIN OF THE UNIVERSE: The Big Bang, that gigantic explosion occurred some 15 billion years ago, is not only the beginning of our own Universe, space, matter and time, but also the generator of all mass. This mass of interstellar cloud of dust and gas (solar nebula) collapsed under its own gravity. The result is, this collapse of molecular clouds vaporized the dusts and the fireball expanded, cooled and compressed in the middle and developed into a Protostar, leaving the rest of the gas to rotate around it.

This cooling effect generated the most basic elements, hydrogen and helium. In due course most of the gases orbiting the forming star flowed inwards towards the star and became part and parcel of it. However, the gases are rotating and therefore due to centrifugal force some of the gases stayed away from the forming star and formed a disc capable of building itself naturally around the forming star. This disc gives away its energy through radiation and cools off into metals, rocks and ice. The dust particles collide and generate bigger particles and this process goes on till the particle builds into the size of a small rocky boulder known as asteroids. Once the bigger of these particles become really large enough to have its own gravity, the growth zooms! Because of gravity, they absorb smaller particles in their orbit and grow substantially. This process, after millions of years got us 10 or more planets in regular habits forming the solar system.