Universal Gravitation Question (solving for distance)

[lindsey0307]

Homework Statement

A space vehicle of mass 555kg, experiences a gravitational pull from Earth of 255N. The mass of Earth is 5.98x10 (to the power of 24) kg.How far is the vehicle a) from the center of the Earth, and b) above the surface of the Earth?

Homework Equations

FG = GM1M2/d squared

The Attempt at a Solution

I rearranged the equation above, and solved for d (the radius) and got the answer 2.95x10(to the power of 7) m, which I believe is correct. However, I can't seem to figure out how to find part b) or even what variable I am solving for. I'm not solving for the radius because I already did that in a) so I think I'll have to alter the equation somehow. Any help would be greatly appreciated!

 

[Doc Al]

I rearranged the equation above, and solved for d (the radius)

d stands for the distance of the object from the center of the earth, not the radius of anything.

However, I can't seem to figure out how to find part b) or even what variable I am solving for.

Hint: What's the radius of the earth? (Look it up.)

 

[technician]

I got the same answer as you for the radius (distance from the centre of the Earth)
To find the height above the surface of the Earth you need to know the radius of the Earth... do you have that?

 

[lindsey0307]

Oh, I just realized I do have the radius of Earth on my formula sheet (which we've never needed to use before). It says it is 6.28x10 (to the power of 6) m.

 

[lindsey0307]

Now I've got the answer! I just subtracted the radius of Earth from my answer in a). Ah, i should've realized that...thank you!