T2 T1 (a) Plan view of camera suspension system All coordinates in feet (-70, 55, 80) (75, 48, 70) Wire 2 Wire 1 Camera Wire 3 (-10, –85, 75) (b)
Two steel wires support a moveable overhead
camera weighing W = 28 lb (see fgure part a) used
for close-up viewing of field action at sporting events.
At some instant, wire 1 is at an angle α = 22° to the
horizontal and wire 2 is at angle β = 40°. Wires 1
and 2 have diameters of 30 and 35 mils, respectively.
(Wire diameters are often expressed in mils; one mil
equals 0.001 in.)
(a) Determine the tensile stresses σ1 and σ2 in the
two wires.
(b) If the stresses in wires 1 and 2 must be the same,
what is the required diameter of wire 1?
(c) To stabilize the camera for windy outdoor conditions,
a third wire is added (see figure part b).
Assume the three wires meet at a common point
coordinates (0, 0, 0) above the camera at the
instant shown in figure part b. Wire 1 is attached
to a support at coordinates (75 ft, 48 ft, 70 ft).
Wire 2 is supported at (270 ft, 55 ft, 80 ft).
Wire 3 is supported at (210 ft, 285 ft, 75 ft).
Assume that all three wires have a diameter of
30 mils. Find the tensile stresses in all three wires.
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