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## Homework Statement

I'm trying to figure out the mass of the earth.

## Homework Equations

I know what it actually is, 5.97*10^24 kg, but it's just

*how*to do it that's got me stumped.

I know the F = Gm1m2/d squared (or r squared depending what you're taught) formula.

## The Attempt at a Solution

I have the mass of my object, which is 0.012kg, i know my d, that's 6.3781*10^3 squared (which is 4.06801586*10^7), I know G (6.67*10^-11), but I'm just confused about the F, in my book we worked it was 931 N = ...., but I think that was just 9.8 N (gravitational acceleration) multiplied by my teacher's weight, as an example.

If I do 0.012*9.8 I get 0.1176 N, so does that mean my equation should look like:

0.1176 N =

__(6.67*10^-11) * 0.012 * Me (mass of earth)__

6.3781*10^3

Then I rearrange the formula to get

__0.1176*(4.06801586*10^7)__

(6.67*10^-11)*0.012

But the answer I keep getting, no matter how many different ways I try, even when I

*do*get the right answer, I'm about 1 000 000 off, i.e. I get 5.97*10^18. WHY oh why is this happening? I have to show working for my assignment. Now I'm lost when I even follow my own book cuz we used different masses i.e. 60 kg instead of 12 GRAMS, (the 12 grams is the weight of my sinker).

Please, please, pleaase any help is REALLY appreciated.