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PROBLEM 3.19
Determine the moment about the origin O of the force F = 4i − 3j + 5k that acts at a Point A. Assume that
the position vector of A is (a) r = 2i + 3j − 4k, (b) r = −8i + 6j − 10k, (c) r = 8i − 6j + 5k.
PROBLEM 3.20
Determine the moment about the origin O of the force F = 2i + 3j − 4k that acts at a Point A. Assume that
the position vector of A is (a) r = 3i − 6j + 5k, (b) r = i − 4j − 2k, (c) r = 4i + 6j − 8k.
PROBLEM 3.21
Before the trunk of a large tree is felled, cables AB and BC are
attached as shown. Knowing that the tensions in cables AB
and BC are 555 N and 660 N, respectively, determine the
moment about O of the resultant force exerted on the tree by
the cables at B.
PROBLEM 3.22
The 12-ft boom AB has a fixed end A. A steel cable is stretched from
the free end B of the boom to a point C located on the vertical wall. If
the tension in the cable is 380 lb, determine the moment about A of the
force exerted by the cable at B.
PROBLEM 3.23
A 200-N force is applied as shown to the bracket ABC.
Determine the moment of the force about A.
PROBLEM 3.24
The wire AE is stretched between the corners A and E of a
bent plate. Knowing that the tension in the wire is 435 N,
determine the moment about O of the force exerted by the
wire (a) on corner A, (b) on corner E.
PROBLEM 3.25
A 6-ft-long fishing rod AB is securely anchored in the sand of a beach. After a fish takes the bait, the
resulting force in the line is 6 lb. Determine the moment about A of the force exerted by the line at B.
PROBLEM 3.26
A precast concrete wall section is temporarily held by two
cables as shown. Knowing that the tension in cable BD is 900
N, determine the moment about Point O of the force exerted by
the cable at B.
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PROBLEM 3.27
In Prob. 3.22, determine the perpendicular distance from point A to
cable BC.
PROBLEM 3.22 The 12-ft boom AB has a fixed end A. A steel cable
is stretched from the free end B of the boom to a point C located on
the vertical wall. If the tension in the cable is 380 lb, determine the
moment about A of the force exerted by the cable at B.
PROBLEM 3.28
In Prob. 3.24, determine the perpendicular distance from point
O to wire AE.
PROBLEM 3.24 The wire AE is stretched between the
corners A and E of a bent plate. Knowing that the tension in
the wire is 435 N, determine the moment about O of the force
exerted by the wire (a) on corner A, (b) on corner E.
