# centroid,centre of mass and centre of gravity

by monty37
Tags: centre, centroid, gravity, mass
 P: 225 may i know what is the difference between centroid,centre of gravity and centre of mass of a body?is it necessary that all the points coincide?
 Mentor P: 11,911 Those all mean the same thing.
P: 181
 Quote by monty37 may i know what is the difference between centroid,centre of gravity and centre of mass of a body?is it necessary that all the points coincide?
Take a triangle for example.

The centroid is the mean position of elements of area.
The centre of mass is the mean position of elements of mass.
In a uniform gravitaional field, the force of gravity on the triangle
can be taken as acting through the centre of mass.

But if the mass per unit area of the triangle varied, the centre of mass
would not (usually) coincide with the centroid.

Note also that the assumption that the earth's gravity is the same
as if its mass were all located at the centre is only true because of
its spherical symmetry.

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