Now observe that the mass of the object - m - is present on both sides of the equal sign. First, both expressions for the force of gravity are set equal to each other.

To understand why the value of g is so location dependent, we will use the two equations above to derive an equation for the value of g.

As one proceeds further from earth's surface - say into a location of orbit about the earth - the value of g changes still. This would result in larger g values at the poles. They also result from the fact that the earth is not truly spherical the earth's surface is further from its center at the equator than it is at the poles. These variations result from the varying density of the geologic structures below each specific surface location. There are slight variations in the value of g about earth's surface. When discussing the acceleration of gravity, it was mentioned that the value of g is dependent upon location. That is to say, the acceleration of gravity on the surface of the earth at sea level is 9.8 m/s 2. In the first equation above, g is referred to as the acceleration of gravity.

Where d represents the distance from the center of the object to the center of the earth. Now in this unit, a second equation has been introduced for calculating the force of gravity with which an object is attracted to the earth. In Unit 2 of The Physics Classroom, an equation was given for determining the force of gravity ( F grav) with which an object of mass m was attracted to the earth F grav = m*g

Gravity formula