The point through which the Whole mass of the body acts, irrespective of the position of the body, is known as centre of gravity (briefly written as c.g.). The plane geometrical figures (like rectangle, triangle, circle etc.) have only areas but no mass. The centre of area of such figures is known as centroid or centre of gravity of the area of the body. It may be noted that every body has one, and only one, centre of gravity.

The centre of gravity of quadrant of a circle lies along its central radius at a distance of 0.6 r.

The point through which the Whole mass of the body acts, irrespective of the position of the body, is known as centre of gravity (briefly written as c.g.). The plane geometrical figures (like rectangle, triangle, circle etc.) have only areas but no mass. The centre of area of such figures is known as centroid or centre of gravity of the area of the body. It may be noted that every body has one, and only one, centre of gravity.

The centre of gravity a T-section 100mmX150mmX50mm from its bottom is 87.5 mm.

Moment of inertia is the
* second moment of force
* second moment of area
* second moment of mass

Mass moment of inertia of a thin rod about its one end is four times the mass moment of inertia of the same rod about its mid-point.