A body of mass m is placed on the surface of earth. Find work required to lift this body by a height
(i). `h=(R_(e))/(1000)`
(ii). `h=R_(e)`

Explanation

(i) `h=(R_(e))/(1000)," as "h lt lt R_(e)`, so we can apply `W_("ext")="mgh",W_("ext")=(m)`
`((GM_(e))/(R_(e)^(2)))((R_(e))/(1000))=(GM_(e)m)/(1000R_(e))`
(ii) `W_("ext")=U_(f)-U_(i)=m(V_(f)-V_(i)),W_("ext")=m`
`[((Gm_(e))/(R_(e)+R_(e)))-(-(GM_(e))/(R_(e)))],W_("ext")=(GM_(e)m)/(2R_(e))`