Strength of Materials (Torsion of Shafts)

Q.1.      For a solid or a hollow shaft subject to a twisting moment T, the torsional shearing stress t at a distance r from the centre will be
            (a)  t = Tr/J
            (b)  t = Tr
            (c)  t = TJ/r
            (d)  none of these
            where J is second moment of area.

Q.2.      A hollow prismatic beam of circular section is subjected to a torsional moment. The maximum shear stress occurs at
            (a)  inner wall of cross section
            (b)  middle of thickness
            (c)  outer surface of shaft
            (d)  none of these (AMIE Winter 1997)

Q.3.      A solid shaft has diameter 80 mm. It is subjected to a torque of 4 KNm. The maximum shear stress induced in the shaft would be
            (a)  75/p N/mm2
            (b)  250/p N/mm2
            (c)  125/p N/mm2
            (d)  150/p N/mm2 (IES 2001)

Q.4.      If in a bar after twisting moment T has been  applied, a line on surface is moved by an angle g then shearing moment will be
            (a)  t/g
            (b)  g
            (c)  g/t
            (d)  none of these

Q.5.      Shear modulus G is given by
             (a)  G = t/g
             (b)  G = g/t
             (c)  G = Tg/t
             (d)  G = T/g

Q.6.      A shaft of length L is subject to a constant twisting moment T along its length L, then angle q through which one end of the bar will twist relative to other will be
            (a)  T/g
            (b)  T/GJ
            (c)  GJ/TL
            (d)  TL/GJ

Q.7.      A circular shaft subjected to torsion undergoes a twist of 10 in a length of 120 cm. If the maximum shear stress induced is limited to 1000 kg/cm2 and if modulus of rigidity G = 0.8 x 106 then the radius of the shaft should be
            (a)  p/8
            (b)  p/27
            (c)  18/p
            (d)  27/p (IES 1993)
            Hint: t/r = Gq/l

Q.8.    At fully plastic twisting moment
            (a)  only fibres at surface are stressed to yield point in shear
            (b)  fibres at centre are stressed to yield point in shear
            (c)  all fibres are stressed to yield point in shear
            (d)  none of these

Q.9.    The relationship among twisting moment(T) acting on a rotating shaft, power in watt(W), and angular velocity in radian per second(w) will be
            (a)  T = W/w
            (b)  W = Tw
            (c)  W = T/w
            (d)  none of these

Q.10.    A shaft turns at 150 rpm under a torque of 1500 N-m. Power transmitted is
            (a)  15p kW
            (b)  10p kW
            (c)  7.5p kW
            (d)  5p kW (IES 1999)
            Hint: P = 2pNT/60

Answers:
1. a
2. c
3. c
4. b
5. a
6. d
7. d
8. c
9. b
10. c

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