Studying the motion of the moon, Newton concluded that the force that causes it to be constantly in orbit is the same as the force that the earth exerts on a nearby body. From there he created the Law of Universal Gravitation.
Newton's Universal Law of Gravitation:
"Two bodies attract each other with force proportional to their masses and inversely proportional to the square of the distance separating their centers of gravity."
F = force of gravitational attraction between the two bodies
G = Universal gravity constant
M e m = body mass
d = distance between the centers of gravity of the bodies.
In the vicinity of the Earth the acceleration of gravity varies, but in the whole lithosphere (life layer) it can be considered constant, its values for some determined altitudes are:
|Altitude (km)||Gravity Acceleration (m / s²)||Altitude Example|
|8,8||9,80||mount everest summit|
|36,6||9,71||highest height reached by manned balloon|
|400||8,70||orbit of a space shuttle|