### Strength of Materials (Torsion of Shafts)

Q.1.     Two steel shafts “A” and “B” are used for transmitting power. The  ratio of revolutions of shafts i.e. NA/NB = 2. The ratio of torques on shafts i.e. TA/TB = 1/2. The ratio of the horse power transmitted by the shafts i.e. PA/PB are
(a)        1/2
(b)        1/4
(c)        1
(d)        2

Q.2.     A twisting moment of 1 kNm is impressed upon a 50 mm diameter shaft, then maximum shear stress will be
(a)        25 MPa
(b)        32 MPa
(c)        37 MPa
(d)        41 MPa

Q.3.     In above problem, what is the angle of twist in a 1 m length of the shaft if G = 85 GNm-2?

Q.4.     There are two shafts of equal length. One shaft is solid having diameter d and another shaft is hollow with inner diameter equal to 3/4 of outer diameter(D). If both shafts are required to transmit a given torsional load then weight of hollow shaft will be ___ % of solid shaft.
(a)        25.7%
(b)        50%
(c)        56.3%
(d)        75%

Q.5.     A hollow steel shaft 3 m long must transmit a torque of 25 kNm. The total angle of twist in this length is not to exceed 2.50 and the allowable shearing stress is 90 MPa. The inside diameter of the shaft will be
(a)        100 mm
(b)        125 mm
(c)        145 mm
(d)        165 mm

Q.6.     In the above problem, the outside diameter of the shaft will be
(a)        145 mm
(b)        165 mm
(c)        175 mm
(d)        200 mm

Q.7.     An axial core of 100 mm is bored throughout the length of a 200 mm diameter solid circular shaft. For the same maximum shear stress, the percentage torque carrying capacity lost by this operation is
(a)        6.25
(b)        12.5
(c)        25
(d)        45        (AMIE Winter 1998)

Q.8.     A composite shaft is fabricated from a 50 mm diameter solid aluminium alloy, G = 30 GNm-2, surrounded by a hollow steel circular shaft of outside diameter 65 mm and inside diameter 50 mm, G = 85 GNm-2. This composite shaft is loaded by a twisting moment of 1.5 kNm, the shearing stress at the outer fibres of the steel will be
(a)        18 MPa
(b)        24 MPa
(c)        30 MPa
(d)        36 MPa

Q.9.     In the above problem, the shearing stress at the outer fibres of aluminium will be
(a)        1 MPa
(b)        2.8 MPa
(c)        5.6 MPa
(d)        9.8 MPa

Q.10.   A hollow shaft has outer diameter 125 mm and inner diameter 75 mm. Shearing stress at the inside fibres is 50 MPa. The shearing stress at the outer fibre will be
(a)        74.7 MPa
(b)        55 MPa
(c)        81.7 MPa
(d)        83.3 MPa

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

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