NEWTON’S LAW OF GRAVITATION

• Every object in the universe attract every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.
• F=F=
• Where G is the constant proportionality and is called the universal gravitation constant. From equation G=
• The value of G is 6.673 x 10^-1N m² kg^-2

ACCELERATION DUE TO GRAVITY

• Galileo was the first to make a systematic study of the motion, of a body under the gravity of the earth.
• He came to the conclusion that “ in the absence of air all bodies will fall at the same rate.
• The acceleration produced in a body on account of the force of gravity is called acceleration due to gravity.
• The value of g at sea – level at a latitude of 45^o is taken as the standard free-fall acceleration (i.e.) g=9.8 ms^-2.

MASS OF THE EARTH

• From the expression g=GM/R² the mass of the Earth can be calculated as follows.

                                             M=9.8 x(6.38 x10⁶)² 6.67 x 10^-11

                                              M=5.98x 10²⁴ kg.