Page 16 - mechanics

Chapter – 3 Concurrent forces in 3D

directed from a point A(xA, yA, zA) to another point

B(xB , yB , zB ) in space, as shown in Figure (3.8). By the head-

to-tail vector addition, we require

rA + r = rB (3.9)

Fig. 3.8 Position vector of point B relative to point A.

Solving for r we get
r = rAB = rB − rA = (xBi + yB j + zBk) − (xAi + yAj + zAk)

So, this relation may be written as
r = rAB = (xB − xA)i + ( yB − yA)j + (zB − zA)k (3.10)

Fig. 3.9 Cartesian components of the position vector rAB.
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