=Tensional Strain.=
Let T = whole tensional strain.
" S = strength per square inch.
" a = sectional area in inches.
Then we have T = Sa.
Now to find the necessary sectional area for resisting any strain, we
have the following general formula:
T
a = ---
S
[TeX: $a = \frac{T}{S}$]
or, by substituting the working strengths for the various materials in
the formula, we have for wood,
a = T/2000