# Ratios involving gravity.

1. Oct 7, 2007

### Rgonzales

1. The problem statement, all variables and given/known data

For this problem, use ratios only to obtain the weight of a person at the following distances. Assume the person weighs 980N on the surface of Earth.

a) 128 000km above the surface of Earth
b) 4.5 times the distance from the centre of Earth
c) 745 400km from Earths Centre.

2. Relevant equations

$$F_{g1} r_1^2 = F_{g2} r_2^2$$

3. The attempt at a solution

I am confused of where numbers should go. I assumed $$F_{g1}$$ to be 980N,
$$r_1^2$$ to be the radius of the earth of 6.38 x 10(to the power of 6), $$r_2^2$$ to be 128 000 km and $$F_{g2}$$ to be the missing variable. Yet, i did not manage to find the answer. Please help me out.