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1. A prybar is used
to remove a nail as
shown. Determine
the moment of the
240 N force about
the point O of
contact between
the prybar and the
small support block.
2. Calculate the moment Mo of the 250 N
force about the base point O of the robot.
3. The spring loaded follower A bears against the circular portion of the cam until the lobe of the cam lifts the plunger. The force required to lift the plunger is proportional to its vertical movement h from its lowest position. For design purposes, determine the angle q for which the moment of the contact force on the cam about the bearing at O is a maximum.
In the exploded view of the contact, neglect the small distance between the actual contact point B and the end C of the lobe.
4. The hydraulic cylinder AB exerts a force F of constant
magnitude 2.5 kN directed from A to B as the engine is
elevated. Determine the moment of F about the point C as a
function of q for the range 0≤ q ≤90o.
W
What is the weight W of the
engine if the combined moment
about C of the force F and
weight W for q =30o is equal to
zero?
5. The pipe assembly is
subjected to an 80 N
force. Determine the
moment of this force
about point A.
6. A 5 N vertical force is applied to the knob of the
window-opener mechanism when the crank BC is
horizontal. Determine the moment of the force about
point A and about line AB.
7. In opening a door which is equipped with a heavy-duty return mechanism, a person exerts a force of magnitude 32 N as shown. Force and the normal n to the face of the door lie in a vertical plane. Compute the moment of about the z axis.
P
P
P
30o
20o 45o 50o
45o
150 mm
A C
D
z
x
y
8. The arms AB and BC of a desk lamp lie in a vertical plane that forms an angle of
30o with xy plane. To reposition the light, a force of magnitude 8 N is applied as
shown. Determine,
a) the moment of the force about point A,
b) the moment of the force about the axis of arm AB,
Direction CD is parallel to the z-axis
and lies in a parallel plane to the
horizontal plane.
mmBCmmAB 325,450
9. Concentrated force is acting perpendicular to the
crank arm BC at point C. For the position q=70°, what is
Mx , the moment of about the x axis? At this instant,
My =-20 N·m and Mz =-37.5 N·m.
150 mm z
x
200 mm
A q
100 mm
B f
O
y
C
P
P
10. Rectangular plate
ADCF is held in
equilibrium by string
AB which has a tension
of T=14 kN.
Determine,
a) The magnitude of
the moment of about
the axis DC,
b) The perpendicular
distance between lines
AB and DC.
z
x
y
A (0, 5, 3) m
E (0, 2, 2)
C (4, 6, 0) m
B (6, 3, 0) m
F
D
O
z
x
y
A (0, 5, 3) m
E (0, 2, 2)
C (4, 6, 0) m
B (6, 3, 0) m
F D
O kjikji
n
nnnkjiT
kjinTT
DC
AFECDC
T
3
1
3
2
3
2
6
244
6412
7
32641
a)
m kN..- M
kjikjinMM
kji
kjijiTrM
M
DC
DCCDC
CBC
DC
6710339812
3
128
3
212
3
218
3
1
3
2
3
2 281218
281218
641232
?
/
z
x
y
A (0, 5, 3) m
E (0, 2, 2)
C (4, 6, 0) m
B (6, 3, 0) m
F D
O
b)
67.58
52.042
22cos ,cos)1(14
3
22
3
22
3
16
3
24
3
212
cos
3
22 , 6412
q
qDCDC
DC
nTnT
kjinkjiT
The parallel component of a force to a line does not
generate moment with respect to that line. If is resolved
into two components parallel and normal to line DC, then
T
mθT
MθTM DC
DC 89.067.58sin14
67.10
sind , dsin
The magnitude of moment MDC is equal to the normal component of to line DC
and the perpendicular distance between and line DC.
T
T