Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

10.5 Pressure and Stress —Force Acting Over an Area 281

Another important geometric property of an object is its second moment of area. As we

explained in Chapter 7, second moment of area provides information on the amount of resis-

tance offered by a member to forces and moments that cause bending. The length also plays an

important role when it comes to bending an object and the stresses that are associated with it.

The force acting on each beam shown in Figure 10.27 will tend to stretch the bottom fibers and

compress the top fibers of the beam. Which beam in Figure 10.27 is easier to bend and why?

Explain.

F

(a)

F

(c)

F

(b)

■Figure 10.27 Simple examples to demonstrate the effect of length and cross-sectional area on bending.

Force

Shear component

of the force

Shear component

of the force

Normal component

of the force

Normal component

of the force

Area

■Figure 10.26

An anchoring plate subjected to a

compressive and a shearing force.

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