GRAVITATIONAL FORCE IMP

                                                        Lesson No :- 1 Gravitation
                                  

           

LESSON NO:- 1 GRAVITATION

       IMPORTANT POINTS

1.       Centripetal Force :- A force act on any object moving along a circle and its directed towards the centre of the circle. This is called centripetal force.

2.        Kepler‘s  First Law :- The orbit of a planet is an ellipse with the sun at one of the foci.

3.     Kepler’s   Second  Law :- The line joining the planet and the sun sweeps equal areas in equal intervals of time.

4.       .  Kepler’s  Third Law :- The square of its period of revolution around the sun is directly proportional  to the cube mean distance of a planet  from the sun.T²/r³ =K.

5.        Newton Universal Law Of Gravitation :- According to this theory , every object in the universe attracts every other object  with a definite force. This force is directly proportional to the product of the masses of the two objects and is inversely proportional to the square of the distance between them.
Fa  M₁M₂/d² or F = Gm₁m₂/d².

6.       Centripetal  Force formula (F) = mv²/r.                                                     
   7.       Earth Gravitational force :- The earth attracts every object  near it towards  itself because of the gravitational force.                                                   
8.       Earth Gravitational Acceleration :- According to Newton’s second law of motion, a force acting on a body results in its acceleration. Thus, the gravitational force due to the earth on a body results in a acceleration. This is called acceleration due to gravity.                                                                       
9.       Variation of value (g):-  (a) Change along the surface of the earth.
(b) Change with height. (c) Change with depth.                                10.    Mass:- Mass is the amount of matter present in the object. The S.I unit of mass is kg. Mass is the  scalar quantity.                                  11.Weight :-  The weight of an object is defined as the force with which the earth attracts objects.                                                                                                           W=F=mg   ….(g=GM/R² )

S.I unit of weight is Newton. It also have a vector quantity.                                12.   Free Fall :- Whenever an object moves under the influence of the force of gravity alone , it is Said to be falling freely.                                            

13.    Gravitational Potential Energy :-  The energy stored in an object because of its position or state is called potential energy.                                           14.     Escape Velocity :- The velocity becomes zero after reaching a certain height and after that the stone starts falling down. Its maximum height depends on its initial velocity.