Physics
posted by Mandy on .
The center of a 1.50 diameter spherical pocket of oil is 1.20 beneath the Earth's surface. Estimate by what percentage directly above the pocket of oil would differ from the expected value of for a uniform Earth? Assume the density of oil is 800 kg/m^3. Solve for delta g/ g = %

do it this way.
you know g for a solid earth.
Now find g for a solid sphere of Earth the size of the bubble, 1.20km away.
Then, find g for a sphere of oil the size of the bubble, 1.20km away.
you have three numbers:
Take the first, subtract the second, and add the third. That is the resultant g value.
Remember in working these fictional bubbles, the mass is volume*density.
g'=GM'/distance^2 where M' is the mass of the bubble (Earth, then oil).