Biomedical Engineering Reference
In-Depth Information
such that the force vector
F
is represented by
⎡
⎣
⎤
⎦
=
⎡
⎣
⎤
⎦
+
⎡
⎣
⎤
⎦
=
⎡
⎣
⎤
⎦
F
x
F
y
F
z
P
x
P
y
P
z
Q
x
Q
y
Q
z
P
x
+
Q
x
∼
=
P
y
+
Q
y
.
(2.57)
P
z
+
Q
z
2.8
Drawing convention
Consider two force vectors,
F
1
and
F
2
, both parallel to the unit vector
e
as
sketched in Fig.
2.12
. In this case the two vectors are identified by numbers
F
1
and
F
2
, rather than by the vector symbols
F
1
and
F
2
. These numbers denote the
magnitude of the force vector, while the orientation of the arrow denotes the direc-
tion of the vector. Consequently this way of drawing and identifying the vectors
implicitly assumes
F
1
=
F
1
e
,
(2.58)
while
F
2
=−
F
2
e
.
(2.59)
This drawing convention is generally used in combination with a certain vector
basis. In this course the Cartesian vector basis is used only. In that case, forces
acting in the horizontal plane, hence in the
e
x
direction, are frequently identified
by
H
i
(from Horizontal), while forces acting in vertical direction, hence in the
e
y
F
1
e
-
F
2
F
2
Figure 2.12
Force vectors identified by their magnitude (
F
1
and
F
2
).
V
3
e
y
H
1
H
2
e
x
Figure 2.13
Force vectors.
