Because the gravitational force
acts toward the center of the Earth, it is parallel to the lifting distance of the object. Thus the infinitesimal work done to lift the object from `r` to `r+dr` is just
`dW = F(r)*dr`
To obtain the total work necessary to lift the object from the center of the Earth to its surface we need to integrate the above expression
`int_0^W dW =int_0^RF(r)dr`
where `R=6371 km` is the Earth radius (given in km).
`W =int_0^6371 0.0015*r*dr =0.0015*r^2/2 (0->6371) =30442.23 J`
The work necessary to lift a mass of 1 kg from the center of the Earth to its surface is 30442 J