Four identical spheres each of mass M and radius 10 cm, each are placed on a horizontal surface touching one another so that their centres are located at the corners of a square of side 20 cm. What is the distance of their centre of mass from centre of any of the spheres?

Options

A. 5 cm
B. 10 cm
C. 20 cm
D. `10sqrt(2)` cm

Answer

D

Explanation

`x_(CM)=(M times 0+M times 20+M times 20+M+0)/(4M)=10cm`
Similarly, `y_(CM)=10cm`
Hence, distance of centre of mass from centre of any one sphere, say
`r=sqrt((10-0)^(2)+(10-0)^(2))=10sqrt(2)cm`