Question

where does the centre of gravity of a sphere and triangular lamina lie ?

Answer 1

of sphere :-

the center of the sphere
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of the triangular lamina :-

the point with the medians meet

Answer 2

The center of the gravity lie where the mass of whole body concentrated at a point which is nothing just called a center of mass...As gravity is tightly linked with mass...

The center of mass of the Geometrical bodies like Ring , Sphere , Square , Rectangle , Triangle etc lies in their Geometrical center...

The geometrical center of Sphere is its Center..Geometrical center of Rectangle and square can be determined by the intersection of their Diagonals...The geometrical center of triangle is the intersection of the Medians called Centeroid..

So center of gravity of Sphere lie at its center and Center of gravity lie at the Centroid of a triangle...