Statics 2e 939
)FCD D 25;000 lb:(6)
Problem 6.101
An end loader for a small garden tractor is shown. All connections are pinned. The only significant weight
is W.
(a)
Draw six FBDs, one each for members
BC
,
DG
, and
AEF
, plate
CDE
, hydraulic cylinder
EG
,
and shovel AB, labeling all forces.
(b)
If the hydraulic cylinder
EG
is capable of producing a
3000 lb
force, determine the largest weight
Wthat may be lifted in the position shown.
Problem 6.102
A trash can weighing
12 lb
has a lid that weighs
4lb
; both weights have
the same line of action, and the weights of all other components are
negligible. A foot-operated lever
ABCD
is used to simultaneously tilt
the can and open the lid, as shown in the inset of the figure. Pin
B
is
attached to the trash can, and it rides in a frictionless slot in lever
ABCD
.
Determine the force
P
required to begin tilting and opening the trash can.
5.5 in./CBn
5.9 in./12 lb .7 in./Hy.15 in./D0; (4)
)BnD32:34 lb;(5)
Problem 6.103
The hoist shown is powered by a motor at point
I
. Cable segment
BE
is
vertical, and segments
EG
and
IB
are horizontal. If
WD10 kN
, determine
the reactions at point
A
, and the force supported by members
CF G
and
DFH
.
Statics 2e 945
Member DFH:
Problem 6.104
A prosthetic arm and hand assembly is shown. Points
B
and
H
are fixed to the
arm. The hand is actuated by a pneumatic cylinder
BF
that opens and closes
the hand. The spring
FH
helps keep the hand in alignment with the arm. If the
person holds a bag of groceries that weighs
30
N and grips the bag at
A
and
D
with a
10
N force, determine the forces supported by the pneumatic cylinder
and the spring. Assume that while holding the bag of groceries, the arm and
hand have the geometry shown where the pneumatic cylinder is horizontal.
Problem 6.105
Three common designs for a bridge to span a multilane highway are shown.
Design 1 is the same as that considered in Example 6.8 on p. 414, where link
CD
is used to connect the two spans of the bridge. Design 2 uses two simply
supported I beams. Design 3 uses a single I beam from points
A
to
E
with
a roller support at midspan. Comment on the pros and cons of each of these
designs, considering issues such as the following:
Which are straightforward to analyze for determining the support reac-
tions and which may be difficult to analyze?
Which may be easier to construct?
Which may be more sensitive to unexpected support motion, such as if
the support at Bsettles with time?
Which may be safer, such as if the support at
B
were accidentally struck
by a vehicle passing under the bridge?
Note: Concept problems are about explanations, not computations.
Problem 6.106
Member
AGB
is a single member with pin connections at points
A
,
G
, and
B
.
Similarly, member
BHC
is a single member with pin connections at points
B
,
H, and C. All other connections are also pins.
(a) Is this structure a truss? Explain.
(b) Determine the forces supported by all truss members.
Problem 6.107
(a) Determine if the truss is statically determinate or indeterminate.
(b) By inspection, identify the zero-force members in the truss.
(c) Regardless of your answer to Part (a), determine the force supported by member QI .
Problem 6.108
(a) Determine if the truss is statically determinate or indeterminate.
(b) By inspection, identify the zero-force members in the truss.
(c) Regardless of your answer to Part (a), determine the force supported by member DG.