CHAPTER-4 GRAVITATION
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 45o 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.