1. Feb 3, 2010

### guitar

the mass of the moon is about 7.5*10^22 kg and its diameter is about 3.5*10^6 meters. calculate the weight of a 70 kg person on the moon.

so we got F=G*m1*m2/d^2

G=6.67*10^-11N*m^2/kg^2

to find the mass we can use m1= F*d^2/m2*G (how did we manipulate the first formula to get this? no matter how i try to change the first formula it never ends up like this one)

i have been trying to solve this for a week now. its not a homework. i am just trying to teach myself physics and this book i purchased is very superficial and leaves huge holes in explanations.

please show me how to solve this. including the manipulations with scientific notation.
thanks.

2. Feb 3, 2010

### rock.freak667

you don't need to find the mass, the force F will give you the person's weight.

3. Feb 3, 2010

### guitar

so i have to use the first formula?

and id like to know how exactly the second formula for m1 was obtained from the first one.

4. Feb 3, 2010

### rock.freak667

Yes.

$$F=\frac{GM_1M_2}{d^2}$$

multiply both sides by d2 and then divide by GM2

5. Feb 17, 2010

### guitar

sorry for a reply long overdue. THANK YOU TONS, especially for breaking down the process of obtaining a formula from another.