A uniform disc of radius R is put over another unifrom disc of radius 2R of the same thickness and density. The peripheries of the two discs touch each other. Locate the centre of mass of the system.

Options

A. at R/3 from the entre of the bigger disc towards the centre of the smaller disc .
B. at R/5 from the centre of the bigger disc towards the centre of the smaller disc
C. at 2R/5 from the centre of the bigger disc towards the centre of the smller disc
D. at 2R /5 from the centre of the smaller disc

Answer

B

Explanation

Distance of C.M from centre of big disc
`x = (r^(2)a)/(R^(2)+r^(2)) , r - ` radius of small disc
R - radius of big disc , a - distance between the centres of discs