Students guide - by Manoj Verma

Unit -12                                 Universe   Unverse: The huge space which contains every things i.e.stars, planets ,satellite, meteorites,  comets etc.   that exist is called the universe .The width of universe is about 100000 light years. Units of astronomical distance :  There are three widely used units to express the astronomical  distance : i)Light year: The total distance covered by a ray  of light in the vacuum in one year is called light year .It is also called  big unit which is used to measure the distance in the universe . Light year =c×t       (Where c = velocity of  light ,t= time taken) =3×10 8 ×60×60×24×365 =9460800 ×10 8  =9.46×10 7 ×10 8 m Therefore ,One light year =9.46×10 15 m ii)Astronomical unit : The distance between the earth and the sun is called astronomical unit .It is also called unit which is used to measure the distance in the solar system . 1 astronomical unit(A.U.)= 1.5 ×10 11 m or 1.5×10 8 km Solar system : The family of the sun includin

                    Physics Unit        -              Topics 7    -         Force and Motion 8     -       Pressure 9     -       Heat 10   -       Wave 11   -       Electricity And Magnetism Unit -  7         Mation and Force Force  : -A physical quantity which change the state of an object is called force. Its S.I. unit  (N).   It is a  vector quantity .  Eg. Pulling force, Gravitational force etc . Force(F) = Mass(m) × acceleration(a)   or  mass(m )× acceleration due to gravity (g) Gravitation or Gravitational force:- The force of attraction between any two heavenly bodies is called gravitational force. Its S. I. unit is  Newton(N) .               Gravitational force(F) = Gm 1 m 2/ d 2 Where m 1 =mass of 1 st  body ,m 2= mass of 2 nd  body ,d=distance between two heavenly bodies. Factors affecting gravitational force:- 1)Mass of 2 heavenly bodies  2)Distance between two object from their center Newton’s law of gravitation:- The force of attraction between two heavenly is  directly