Gravitational mechanics:
Mechanics is branch of physics which is concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effect of bodies on their environment.
Isaac Newton focused much of his work on the theory of gravitation force and the effect of it on the orbit of the planets.
Energy which is stored in the gravitational field is called as gravitational potential energy, or potential energy due to gravity.
Let's see how energy gets stored in the gravitational field. Firstly, remember that work equals force times distance as stated in this formula:
W = F . d
Several decades after discovery of general relativity it was realized that the general relativity is incompatible with quantum mechanics. It is possible to describe gravity in the framework of quantum field theory like the other fundamental forces, such that the attractive force of gravity arises because of exchange of virtual gravitons, in the same way as the electromagnetic force occurs from exchange of virtual photons. This reproduces relativity in the classical limit. However, this approach fails at short distances of order of Planck length, where a more complete theory of quantum gravity is required. Many believe the complete theory to be string theory, or currently M-theory, and, on the other hand, it can be a background independent theory like loop quantum gravity or causal dynamical triangulation.
The work has been done lifting the object, and the energy has been stored in the gravitational field the potential energy can be released by dropping the object. As it falls its height above ground gets less, so, the potential energy stored in gravity gets less and less, also. The object, though, is speeding up in the way as it falls.
Kinetic energy is the energy of motion. As object falls it travels faster, and therefore, picks up more and more kinetic energy. This increase in kinetic energy during the fall is because of drop in gravitational potential energy during the fall. The gravitational potential energy becomes kinetic energy of the falling object.
As the universe M expands, potential energy PE of (M-m),relative to mass m, decreases and as the total energy of the universe is a constant, the kinetic energy of the mass m, relative to the rest of the universe (M-m), should increase. This is accomplished by the acceleration of mass m. In an equilibrium state of an expanding universe, mass m is accelerating continually relative to the center of mass of the effective universe, by rotation or revolution about that center of this mass. This is called as mass of it. MASS m said to be the result of the effect of the expansion of the rest of the universe on the density of the energy of m. Mass m exists due to the expansion of the universe relative to the mass m . It has been computed that, at equilibrium, the values of KE and PE are nearly the same and the planets and moons travel in circular orbits at a distance L from the center of mass. Two bodies attract each other with equal and opposite forces; the magnitude of this force is proportional to the product of the 2 masses and is also proportional to the product of the 2 masses and is also proportional to the inverse square o the distance between the centers of mass of the 2 bodies.
F = G. M. m / r2
here m and M are the masses of the 2 bodies, r is the distance between the 2, and G is the gravitational constant, whose value can be given by:
G = 6.67. 10-11 Newton.metre2/kg2
force with which the Earth attracts bodies situated near to its surface is called as body's weight.The weight of mass m, which is located on the Earth's surface, can be given by:
P = m. g
this expression is an immediate consequence of Universal Gravitation Law and of Newton's Second Law.Under the normal conditions, value of g is approximately equal to 9.8 meters/second.