other words, equation ( . ) implies that the gravitational field at a point is equivalent to the acceleration experienced by a particle at that point. However, it is to be noted that a and E are separate physical quantities that have the same magnitude and direction. The gravitational field E is the property of the source and acceleration a is the effect experienced by the test mass (unit mass) which is placed in the gravitational field E .
The non- contact interaction between two masses can now be explained using the concept of “Gravitational field”. Points to be noted: i) The strength of the gravitational field decreases as we move away from the mass M as depicted in the Figure . . The magnitude of E decreases as the distance r increases.
Figure . Strength of the Gravitational field lines decreases with distance Q Figure . shows that the strength of the gravitational field at points P, Q, and R is given by Q < < . It can be understood by comparing the length of the vectors at points P, Q, and R.
ii) The “field” concept was introduced as a mathematical tool to calculate gravitational interaction. Later it was found that field is a real physical quantity and it carries energy and momentum in - - - - Unit Gravitation space. The concept of field is inevitable in understanding the behavior of charges. iii) The unit of gravitational field is Newton per kilogram (N/kg) or m s - .
. . Superposition principle for Gravitational field Consider ‘n’ particles of masses m m m n , , , distributed in space at positions … r r r , , etc, with respect to point P. The total gravitational field at a point P due to all the masses is given by the vector sum of the gravitational field due to the individual masses (Figure .
). This principle is known as superposition of gravitational fields. total n = - - - -