\fdO'^ - Old Forge Coal Mines

(575)
STRENGTH OF MATERIALS.
See Arts. 1 1 33 to 1 1 37.
215
(576) See Fig. 49. The force polygon 0-1-2-3-^-0 is
drawn as in Fig. 47, 0-4 being the resultant. The equilibrium
polygon ab c d g a g^^i^ ^f f^^^^^ JZ50 lb.
is then drawn, the
Scale of distance I'^S"
point g" lying on the
resultant. The resultant
R is drawn
through g, parallel to
and equal to O-4. A
line is drawn through
C, parallel to R.
Through g the lines
ge and g/ are drawn
parallel, respectively,
to PO and P4, and
intersecting the parallel
to R, through C
in e and / ; then, e/
is the intercept, and
Pu^ perpendicular to
0-4, is the pole distance.
Pii = d3lh.;
^/=1.32'. Hence,
the resultant mo- FiG. 49.
ment is 33 X 1.32 = 43.6 in. -lb. Ans.
,/. /.
(577) The maximum bending moment, M= W-^ (see
Fig. 6 of table of Bending Moments) = 4 X 2,000 X "^^ ^ ^ =
40,727tV ft.-lb. =488,727 in.-lb. Then, according to formula
74,
ST = 488,727.
fc
/ 488,727/ 488,727X8 ,.,,,„,
7 = = = ^'^^•^^*-
S,
9,000