Question

At which point is the centre of gravity situated in: A circular lamina.
  A. At the centre of radius
  B. At the centre of semicircular lamina
  C. At the centre of circular lamina
  D. cannot say

Answer 1

Hint According to the question, first we have to check whether the body is regular or irregular. Then we have to compare between centre of mass and centre of gravity. If regular, the centre of gravity is the same as the centre of mass.

Complete Step by step solution
As we know, any circular shape such as a lamina ring is a regular shaped body (or we can call this a uniform) because the radius of a circular body is the same at any point of edges of that particular circular body. And the centre of gravity is always situated in the centre of the circular body. And if the body is irregular, then the centre of mass of the body is not the same as the centre of gravity, and the centre of gravity never lies on the centre of that particular irregular body.
Centre of gravity means a point from which the mass of a body or system may be considered to act. Moment of mass of a ring about this point is zero. In uniform gravity, the centre is the same as the centre of the mass. And for uniform shapes, the Centre of mass is their gravitational centre. Hence, the centre of gravity is situated at the centre of circular lamina.

Hence, the correct option is (C). At the centre of circular lamina.

Note In humans, the centre of gravity changes as the person moves and bends. The act of balancing requires maintenance of the centre of gravity above the feet. A person falls when his centre of gravity is displaced beyond the position of the feet.