How Does Distance from Earth's Center Affect Gravity?

AI Thread Summary
The discussion focuses on calculating the force of gravity on an astronaut at a distance of 2 meters from Earth's center, given a surface gravity force of 634N. Participants suggest using the gravitational force equation F=Gm1m2/r^2 and recommend expressing the forces as a ratio to simplify the problem. The ratio Fa/Fb is proposed, where Fb is the force at the surface and Fa is the force at twice the radius. Clarification is sought on how to properly set up the equations and simplify them. The conversation emphasizes the importance of understanding the relationship between distance from Earth's center and gravitational force.
King Khan
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Homework Statement


The force of gravity at Earth's surface on an astronaut if 634N. What is the force of gravity on the same person if the distance is 2m, in multiplies of Earth's radius, from the center of Earth?

Homework Equations


F=Gm1m2/r^2

The Attempt at a Solution


I really don't understand what to plug in where seeing as how they don't even give the mass, if someone could just please help me with this part I could do the rest.
 
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Why don't you write it as a ratio of two forces and see if anything cancels.

Fa/Fb

Where Fb is the force at the surface and Fa is the force at twice the radius.
 
DaleSpam said:
Why don't you write it as a ratio of two forces and see if anything cancels.

Fa/Fb

Where Fb is the force at the surface and Fa is the force at twice the radius.
if you could rephrase that, sorry but I really don't understand.
 
F_a=\frac{G \, m1_a \, m2_a}{r_a^2}
F_b=\frac{G \, m1_b \, m2_b}{r_b^2}
Write Fa/Fb, simplify and solve.
 

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