A superconducting gravity meter can measure changes in gravity of the order = 1×10-11 (delta g)/g. You are hiding behind a tree holding the meter, and your 78 kg friend approaches the tree from the other side. How close to you can your friend get before the meter detects a change in g due to his presence?
Answer in units of m.
I know that Fgrav = G (m1m2)/r^2 and G = 6.672e-11 Nm^2/kg^2
The Attempt at a Solution
My first thought was to assume the m2 was 1kg and set the Fgrav = 1e-11 N, but this was wrong.