1.

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)`

Answer» (i). `h=(R_(e))/(1000)` as `hltltR_(e)` so we apply `W_(ext)=mgh`
`W_(ext)=(m)((GM_(e))/(R_(e)^(2)))((R_(e))/(1000))=(GM_(e)m)/(1000R_(e))`
(ii). `h=R_(e)` in this case h is not very less than `R_(e)` so we cannot apply `DeltaU=mgh`
`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))`


Discussion

No Comment Found

Related InterviewSolutions