(a) Suppose, the mass of circular disc is M. A square portion of diagonal r is cut from it. Assuming centre of mass of circle to be origin. Centre of mass of square portion will be at distance
r
2
from it. ∴ Side of square =
r
√2
Area of square =(
r
√2
)2=
r2
2
Mass of square, m=M×
r2∕2
πr2
m=
M
2π
Centre of a mass of remaining disc from the centre of disc, x=M×0−