Doubt from Gravitation


From a uniform solid sphere of radius R , a sphere of radius R/2 is removed and taken to infinity . The work required by external agent to achieve this is ? Take original mass as M . Tanmay Sir , Pratyaksh Sir


Anyone ?? Tanmay sir , Ayan sir ,Sneha ..


This one too Tanmay Sir .


Work done is change in Potential energy of system, final PE =0 and initially it was self energy of the uniform solid sphere that is
W = \frac{-3GM^2}{5R}

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How final PE=0?
Only the interaction energy between the two will be zero, but still the self energy of sphere with cavity and a sphere of radius R/2 exists.
@pratyaksh_2019 please correct me if I'm wrong.


yeah my bad


Anyone ?? Pls solve


Pratyaksh sir , Tanmay Sir




Pls check the answer i have tried to solve.Tanmay


Sir sry but answer is wrong


Can any student ask their coaching teachers about this problem ??


centre of mass of big sphere got changed due to carving out of
Sphere of radius R/2 so distance between two sphere shouldnot be R/2 it got changed.
So let me try to incorporate it in the problem and the lower limit of intregation should be changed. Ok let me try



Tanmay Sir sry this one is too wrong , actually question was this :

answer given is 5 , pls help.others Ayan sir , Sonu , Samarth , Sneha