Unit Vectors
Instead of explicitly writing Ax = 5, Ay = 0; Bx = 5, By = 5; Cx = - 10, Cy = 0; and Dx = - 5, Dy = 5, we can write this same information in a different form. We can write
A = 5 i + 0 j B = 5 i + 5 j
C = - 10 i + 0 j
D = - 5 i + 5 j
i and j are "unit vectors" in the x- and y-directions. Being "unit vectors", they each have a magnitude of one. They carry only the direction information.
Now we can write
R = A + B + C + D R = (5 i + 0 j) + (5 i + 5 j) + (- 10 i + 0 j) + (- 5 i + 5 j)
R = ( 5 + 5 - 10 - 5 ) i + ( 0 + 5 + 0 + 5 ) j
R = - 5 i + 10 j
Now we know the components of the resultant,
Rx = - 5 and
Ry = 10 and we can proceed exactly as before to recombine those to find the magnitude and the direction.
To explicitly remind ourselves that i and j are "unit vectors", they are sometimes (or oftentimes) written with a "hat" or "caret" above them,
Vector Components Displacement, Velocity, and Acceleration Return to ToC, Vectors (c) 2005, Doug Davis; all rights reserved