# Gravity problem

#### physicshard22

1. The problem statement, all variables and given/known data
Determine the distance from earth's centre where the force of gravity acting on a space probe is only 11% of the force acting on the same probe at the earth's surface. express your answer in terms of earth's radius,

2. Relevant equations
F = Gm1m2/R^2

3. The attempt at a solution
i tried plugging in the values but i cant seem to get the answer

Last edited:
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#### ideasrule

Homework Helper
Write down two versions of the gravitation equation:

Fs=Gm1m2/R^2
Fp=Gm1m2/r^2

where Fs is the force of gravity on Earth's surface and Fp is the force of gravity put in space. Fp/Fs = 0.11, as the question states. See what you can do with that.

#### rl.bhat

Homework Helper
The relevant equation given by you is for the force on the surface of the earth. If h is the distance of the probe from the earth's surface, what is its distance from the center of the earth? What is the force on it? take the ratio of these forces and equate it to the given value and solve for h.

#### physicshard22

i don't understand

h/h' = 0.11?

then what can i do?

#### rl.bhat

Homework Helper
terms of R, what is h and h' for Fs and Fp?

#### rl.bhat

Homework Helper
h = 1r
h' = 2r
No.
h is r and h' = r + H where H is the height of the probe from the surface of the earth. find H.

#### physicshard22

so it would be r/r+h = 0.11?
how do i solve with 2 unknowns?

#### rl.bhat

Homework Helper
You have to write h in terms of r.

#### physicshard22

this is so confusing can you give me another hint?

#### physicshard22

Did anyone get the answer so i can compare?

#### bleedblue1234

give us the radius and mass of earth ur using

#### physicshard22

The question doesn't give it

#### rl.bhat

Homework Helper
r/(r+h) = 0.11
r = 0.11(r+h)
Now simplify and find h.

"Gravity problem"

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