Effect of Gravity on Falling Objects

I have and important lesson to share with you all that is all about effects of gravity on falling objects.
Acceleration Due to Gravity of the Earth -
Gravity of the earth can be imagined to be a sphere made of a large number of concentric spherical shells with the smallest one at the center and the largest one at its surface. A point outside the earth is obviously outside all the shells. Thus, all the shells exert a gravitational force at the point outside just as if their masses are concentrated at their common center according to the result stated in the last section. The total mass of all the shells combined is just the mass of the earth. Hence, at a point outside the earth, the gravitational force is just as if its entire mass of the earth is concentrated at its center.
Gravitational Potential Energy -
The force of gravity is a conservative force and we can calculate the potential energy of a body arising out of this force, called the gravitational potential energy.
Weightlessness -
Weight of an object is the force with which the earth attracts it. We are conscious of our own weight when we stand on a surface, since the surface exerts a force opposite to our weight to keep us at rest.
Newton’s law of universal gravitation states that the gravitational force of attraction
between any two particles of masses m1 and m2 separated by a distance r has the magnitude
where G is the universal gravitational constant, which has the value 6.672 ×10–11 N m2 kg–2.
This was just and introduction to Effects of Gravity. Keep reading ... will discuss more on physics help may be in next lesson