In this post, we will discuss and derive **the formula for the **acceleration due to gravity at height h (where h<<Radius of the earth). As height or altitude from the earth’s surface increases the value of g falls. Now we are to discuss and derive the equation of g that describes this change in g with the increase in height.

**The formula for the acceleration due to gravity at height h**

The **formula for the acceleration due to gravity at height h** (where h<<R) is expressed by the formula:**g1 = g (1 – 2h/R)**.

Here g1 is the acceleration due to gravity at height h and R is the radius of the earth.

g denotes acceleration due to gravity on the earth’s surface.**For example, considering g = 9.8 m/s^2 on the earth’s surface, g1 at a height of 1000 meters from the surface of the earth becomes 9.7969 m/s^2.*** [ ***check with online calculator*** ]*

**Derive the Formula for acceleration due to gravity at height h**

This section covers the variation of g with altitude. At a height of h from the surface of the earth, the gravitational force on an object of mass m is

F = GMm/(R+h)^{2}

Here (R + h) is the distance between the object and the center of the earth.

Say at that height h, the gravitational acceleration is g1.

So we can write, mg1 = GMm / (R+h)^{2}

=> g1 = GM/(R+h)^{2} _________________ (1)

Now we know on the surface of the earth, it is

g = GM / R^{2} [ see the proof: **equation of g on earth’s surface** ]

Taking the ratio of these 2,

g1/g = R^{2} /(R+h)^{2}

=> g1/g= 1/(1 + h/R)^{2} = (1 + h/R)^{-2} = (1 – 2h/R) *[ with the apprroximation that h<<R]*

so,** g1/g = (1 – 2h/R)**

** The Formula for acceleration due to gravity at height h** is represented with this equation:

**=> g1 = g (1 – 2h/R) ______(2)**(where

*h<<R*)

g1 is acceleration due to gravity at height h.

**Use our online calculator to test the equation. Click the image below for the calculator page.** use for heights where h<<Radius of the earth.