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454 Solutions Manual
TBE
18
23 CRBx D0; (15)
13
Statics 2e 455
Problem 3.142
Bead
C
has
2lb
weight and slides without friction on straight bar
AB
. The
tensile forces in elastic cords
CD
and
CE
are 0.5 and
1:5 lb
, respectively. If
the bead is released from the position shown with no initial velocity, will it slide
toward point Aor Bor will it remain stationary?
C0:5 lb .3/.12/ C.12/.16/ C.4/.15/
.13/.25/
(7)
Problem 3.143
Bead
C
has
2lb
weight and slides without friction on straight bar
AB
, and
the tensile force in elastic cord
CE
is
0:9 lb
. Determine the force needed in
cord
CD
for the bead to be in equilibrium, and the magnitude of the reaction
between the bead and bar AB.
Problem 3.144
A hoist for lifting objects onto and off a truck is shown. All cables
lie in the
xy
plane, cable segment
AB
is horizontal, and the plane
formed by bars
CE
and
CF
is parallel to the
y´
plane. Pulleys
are frictionless and force
P
is vertical. If the object is being
slowly lifted and weighs
WD600 lb
, determine the force
P
and
forces supported by all cables and bars.
Problem 3.145
For Prob. 3.144, determine the largest weight
W
that may be
lifted if forces supported by the cables may not exceed
2000 lb
and compressive forces supported by the bars may not exceed
2800 lb.
Problem 3.146
The structure shown in Fig. P3.146(a) consists of a steel I beam
AB
and a steel
cable
AC
, and load
P
is horizontal. For the geometry and loading shown, the
cable will likely be considerably more flexible than the I beam, and the structure
shown in Fig. P3.146(b) is an appropriate model where the I beam is rigid and
the cable is a spring with stiffness kD2000 lb=in.
(a)
Let
PD5000 lb
, and assume the displacement of the structure is small.
Thus, using the geometry shown in Fig. P3.146(b) where the I beam is
vertical and the cable has 45
ı
orientation, determine the forces supported
by the I beam and cable. Using these forces, determine the horizontal
displacement
d
of point
A
, assuming the spring is unstretched when the
I beam is vertical.
(b)
Let
dD4in:
; for this case the I beam is no longer vertical and the cable’s
orientation is no longer 45
ı
. Determine the force
P
needed to produce
this value of
d
, assuming the spring is unstretched when the I beam is
vertical.
(c)
Comparing the analyses in Parts (a) and (b), which of these provides the
more accurate results (explain)?
CB
d
A
100 in.
145.0 in.
100 in.
Dcos1.100 in./2.145:0 in./2.100 in./2
2.145:0 in./.100 in./D43:55ı:(7)
Cd 4 in.
B
100 in.
90°
D144:2 in. (13)
XFxD0W TAC cos TAB sin ˛CPD0; (18)
