# Gravitational field strength formula

1. May 9, 2005

### g33n13

Q: "The Earths radius is 6700km. Show that the magnitude of the gravitational field strength at a height of 350km above the Earth's surface is about 9 N/kg"

I got the mass of the Earth which is 5.98E 24
G the constant = 6.67E -11

Formula : g= GM/r² , i cant seem to get 9, am I supposed to use the 350km??

2. May 9, 2005

### whozum

Yeah, at a distance R away, the gravitational force is

$$mg = \frac{GMm}{r^2}$$

Your distance R is 350km above the earth's surface .

3. Sep 22, 2011

### jimmyjammy

Make sure your 350km is in metres!