The centre of mass of two masses $m$ and $m'$ moves by distance $\frac{x}{5}$ when mass $m$ is moved by distance $x$ and $m'$ is kept fixed. The ratio $\frac{m'}{m}$ is

In general form what are the coordinates of centre of mass of a rigid body.

From a uniform disc of radius $R$, an equilateral triangle of side $\sqrt 3 \,R$ is cut as shown. The new position of centre of mass is :

Two objects of mass $10\,kg$ and $20\,kg$ respectively are connected to the two ends of a rigid rod of length $10\,m$ with negligible mass. The distance of the center of mass of the system from the $10\,kg$ mass is :

Four particle of masses $m, 2m, 3m$ and $4m$ are arranged at the corners of a parallelogram with each side equal to $a$ and one of the angle between two adjacent sides is $60^o$. The parallelogram lies in the $x-y$ plane with mass m at the origin and $4m$ on the  $x-$ axis. The centre of mass of the arrangement will be located at 

Two semicircular rings of linear mass densities $\lambda $ and $3\lambda $ and of radius $R$ each are joining to form a complete ring. The distance of the centre of the mass of complete ring from its geometrical centre is