What is First Moment of Area?

In this article we will discuss about definition of first
moment of area or moment of area, application and example. We will also derive
the formula for it.

First Moment of Area

Considered a thick lamina or a body having area A. let x is
the distance of C.G. of the area from the axis OY and y is the distance of C.G.
of the area from the axis OX.
First Moment of Area
Here
x = Distance of C.G. of area A from axis OY
y = Distance of C.G. of area A from axis OX
Then,
First Moment of Area Formula

This equation (1) is known as the first
moment of area about the axis OY

Similarly
First Moment of Area Formula

This Equation (2) is called the first
moment of area about the axis OX.

Conclusion:

First moment of area/moment of area:

The first moment of area of a lamina
about an axis is defined as the product of area of the lamina and the
perpendicular distance of the C.G. of the area form the axis.

Application

It is used to determine the center of
gravity of area.

Numerical Example

If we have a lamina having
area 10 cm2 and the distance of its C.G from the axis are shown in
the figure given below.
First Moment of Area Example
Then
The first moment of area about axis OY =
10 x 5 = 50
The first moment of area about axis OX =
10 x 7 = 70
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Pankaj Mishra

Pankaj Mishra is a blogger by passion and Mechanical Engineer by profession. He has completed his B.Tech degree in mechanical engineering in the year 2015. He loves to share his knowledge and help others.

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