Question

One end of a steel wire of area of
cross-section 3 mm2 is attached to the
ceiling of an elevator moving up with an
acceleration of 2.2 m/s2. If a load of 8 kg is
attached at its free end, then the stress
developed in the wire will be
(a) 8 x 106 N/m (b) 16 x 106 N/m2
(c)20 x 106 N/m2 (d) 32 x 106 N/m2
​

Answer 1

Answer:

STRESS=FORCE/AREA. As in a escalator accelerating upward, tension in string is T=mg-ma, T=8(10-2.2)=8x7.8.

STRESS=8x7.8/3x10-6. STRESS=20.8x106 N/m2.

Answer 2

Answer:

32*10^6n/m^2

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