Centre of Gravity
The centre of gravity (C.G) of an object is the point through which its whole weight appears to act for any orientation of the object.
The centre of mass of an object is the point which its entire mass seems to act.
C.G of an object depends on the distribution of its mass.
For a regular shaped object, C.G is at its geometrical centre.
For an irregular shaped object, C.G can be determined by plumb line method.
Step 1: Suspend the lamina at one point with plumb line;
Step 2: Trace the straight line formed by plumb line when lamina is steady;
Step 3: Repeat for two more points
Step 4: The point of intersection of the three lines is the position of C.G.
(1) Plumb line method can also be used to determine C.G of regular shaped object.
(2) C.G may also lie outside the object, like ring.