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Fig. 2-22.

Position. The position vector r in Fig. 2-22 specifies the
A
location of the “base point” A, and the relative-position vector r / BA
locates point B with respect to point A. By vector addition, the
position of B is then
r B = r A + r / BA . 2-79
Displacement. During an instant of time dt, points A and B
undergo displacements dr and dr as shown in Fig. 2-23,a. If we
B
A
consider the general plane motion by its component parts then the

a b
Fig. 2-23.

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