Page 13 - ebook fluid mechanics_finalize
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FLUID MECHANICS
1.1.1 Define the Fluid
A fluid is a substance which can deforms continuously when being subjected to
shear stress at any magnitude, however small they may be. Conversely, if a fluid is
at rest, there can be no shearing forces acting and, therefore, all forces in the fluid
must be perpendicular to the planes upon which they act. When the fluid is in
motion shear stress are developed if the particles of the fluid move relative to each
other. When this happens adjacent particles have different velocities, causing the
shape of the fluid to become distorted. Refer Figure below for the illustration.
Figure 1.1 : Illustration Of Shear Force Acting at Fluid
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