# help with physics

• Oct 10th 2012, 05:47 PM
Louisana1
help with physics
A 650 kg satellite orbits at a distance from the Earth's center of about 7.2 Earth radii. What gravitational force does the Earth exert on the satellite?

how would I set this up and what equation would I use
• Oct 10th 2012, 06:41 PM
MarkFL
Re: help with physics
Use Newton's law of gravity:

$F=G\frac{m_1m_2}{r^2}$

or find the weight of the satellite at the surface of the Earth, then use the fact that the force due to gravity varies inversely as the square of the distance from the center of the Earth. This method is easiest, as you don't need to use Newton's gravitation constant, or know the mass and radius of the Earth.
• Oct 11th 2012, 03:23 PM
Louisana1
Re: help with physics
What? How do you write that?
• Oct 11th 2012, 04:44 PM
skeeter
Re: help with physics
Quote:

Originally Posted by Louisana1
What? How do you write that?

$\frac{650 \cdot 9.8}{7.2^2}$