Gravitational Force of Meteor and Earth: 1/8 vs 64 Times as Distance Changes

[zelda1850]

Homework Statement

As a meteor moves from a distance of 16 Earth radii to a distance of 2 eath radii from the center of earth, the magnitude of the gravitational force between the meteor and Earth becomes

1) 1/8 as great
2) 8 times as great
3) 64 times as great
4) 4 times as great

Homework Equations

i think there's an equation to it but i don't know

The Attempt at a Solution

i know that double the radius is 4 times the force but I am not sure how to answer this question

 

[Dick]

The equation you want is called 'Newton's law of universal gravitation'. It's really pretty famous. Can you try and find it?

 

[zelda1850]

oh is choice 3 correct?

 

[Dick]

I would feel better answering that if you explain why you think so.

 

[zelda1850]

emm i did 16 square divided by 2 square and got 64

 

[Dick]

That's good. It's right.

 

[zelda1850]

oh thanks for the help