Gravitational Fields

[mcmerc01]

Hello,

Here's my question that I pose to you.

100kg meteor is falling toward the earth from a distance of 4.0 Earth Radii from the center of the earth (4.0R_E)

1. Calculate g at this height.
Ok, so, the equation we use here is g=GM/R² where G=6.67x10^-11 and we know the mass of the earth is 5.98x10²⁴kg.  The radius of the earth is 6.38x10⁶m.

So first would we work out the distance that 4 earth radii is? Which is 4 x radius of the earth (6.38x10⁶?  <-- I've done this and gotten 2.55 x 10⁷ and subbed that into the equation g=GM/R² giving me an answer of... 0.613N Kg^-1 Does this seem correct?

That is the only part I am not 100% sure on. Once we know this, we can sub it back into the equation and should get g in N Kg^-1.

2. Acceleration of Meteor at this height.
It is falling down, so acceleration is g. assuming above is correct, 0.56ms^-2 down.
3. Ratio: acceleration at 4.0R_E/2.0R_E
I'm not great with this, could someone fill me in on ratios and what not?

For now, I pose these questions, more will follow

[yellowsone31]

maybe use the inverse square law?

[mcmerc01]

hmmmm well, I am going to sound stupid now, but what is the inverse square law? I can't remember it!

And how would I apply it? And where do I use it? for which part? the Ratio?

NO WAIT! I think i remember the inverse square law. ..... but no I lost it.

[Lasercookie]

For question 3. acceleration at 4.0RE/acceleration at 2.0RE









(the GM's and R^2 cancel)

[mcmerc01]

Thanks a lot

I get the ratios thingy now. I'll post some more if I have trouble!!!