# Finding altitude of a satellite if you know it's radius and mass

## Homework Statement

A 135 kg satellite experiences a gravitational force by the Earth of 960 N. What is the radius of the satellite's orbit. And altitude? I already found the radius and I came up with 7489.99 km. I just need help finding the altitude.

## Homework Equations

Equation for period: T= 2∏ times the square root of (r^3) / (GMe)
Period= how long it takes to go around once.
From this step what do I do next?

## The Attempt at a Solution

For T I did 2∏ times the square root of (4.2E11) / (3.99E14)

I got 4.2E11 but taking the radius I got up above (7489.99) and then curbing it. I got 3.99E14 by taking G (6.67E-11) times Me (5.98E24).

## Answers and Replies

SteamKing
Staff Emeritus
Science Advisor
Homework Helper
What is the definition of altitude?

If you know the radius of the orbit about the earth, what other number do you need to know to calculate altitude?

Altitude=the height of an object. I also need to know the speed of the orbit?

D H
Staff Emeritus
Science Advisor
You do not need to know the object's orbital velocity.

Altitude is the height of the object above what?

I need to know the objects radius?

D H
Staff Emeritus
Science Advisor
No. You are missing something very basic. What is the satellite orbiting?

SteamKing
Staff Emeritus
Science Advisor
Homework Helper
Altitude=the height of an object. I also need to know the speed of the orbit?

Height of an object relative to what? The center of the earth? The upper shelf in your closet? The top of the Empire State Building?

The satellite is Orbiting earth...

D H
Staff Emeritus
Science Advisor
You already know the distance from the center of the Earth to the satellite. So how far is the satellite above the surface of the Earth?