Question 7. 16. From a uniform disk of radius R, a circular hole of radius R/2 is cut out. The centre of the hole is at R/2 from the centre of the original disc. Locate the centre of gravity of the resulting flat body.


Let σ is the mass per unit area.
Total mass,m =σπr2
Mass of smaller disc=σπr22=m4

Centre of mass of the disc,
xcm =m1r1+m2r2m1+m2
=m×0-m4×r2m-m4
=-r6
Hence the centre of mass is shifted   r6   leftward from point O.