Cavities below the surface of the Earth cause anomalies in the value of g measured at the surface.
a) Show that the vertical component of g a distance x from a point directly above a cavity is less than would be expected, assuming a uniform rock density of r=2.8 g/cm3, by the amount
b) Plot as a function of x<2000 m for a spherical cavern 50 m in radius 500 m below the surface.