Unformatted text preview: 01Ch01.qxd 6 9/25/08 7:49 PM Page 6 CHAPTER 1 Tension, Compression, and Shear Problem 1.2-6 A car weighing 130 kN when fully loaded is
pulled slowly up a steep inclined track by a steel cable (see figure).
The cable has an effective cross-sectional area of 490 mm2, and the
angle a of the incline is 30°.
Calculate the tensile stress st in the cable. Solution 1.2-6 Car on inclined track
FREE-BODY DIAGRAM OF CAR TENSILE STRESS IN THE CABLE
W Weight of car T Tensile force
R1, R2 Effective area
of cable Wheel reactions (no friction force between
wheels and rails) st T
A Wsin a
A SUBSTITUTE NUMERICAL VALUES:
st 130 kN 30°
2 490 mm (130 kN)(sin 30°)
133 MPa ; EQUILIBRIUM IN THE INCLINED DIRECTION
T 0 Q+b T W sin a 0 W sin Problem 1.2-7 Two steel wires support a moveable overhead
camera weighing W 25 lb (see figure) used for close-up
viewing of field action at sporting events. At some instant, wire 1
20° to the horizontal and wire 2 is at an angle
is at on angle
48°. Both wires have a diameter of 30 mils. (Wire diameters
are often expressed in mils; one mil equals 0.001 in.)
Determine the tensile stresses 1 and 2 in the two wires. T2 T1 b a W ...
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