Locate the centre of mass of a uniform hemi spherical shell of radius R with reference to point 0 {as shown in figure}
Figure shows a hollow hemisphere of mass M and radius R. Now we consider an elemental circular strip of angular width dθat an angular distance dθ from the base of the hemisphere. this strip will have an area ds=2πRcosθRdθ
Its mass dm is given asdm=M2πR22πRcosθRdθHere y−coordinate of this strip of mass dm can be taken as Rsinθ.Now we can obtain in the centre of mass of the system asycm=1M∫π20dm Rsinθ=1M∫π20M2πR22πRcosθ Rdθ Rsinθ=R∫π20sinθcosθdθycm=R2