21) A shaft subjected to pure torsion is to be designed which of the following theories gives the largest diameter of shaft?
a) Maximum principal stress
b) Maximum shear stress theory
c) strain energy theory
d) All the above theories give same diameter
22) The radius of Mohr’s circle of stress of a strained element is 20 N/mm2 and minor principal tensile stress is 10 N/mm2. The major principal stress is
a) 30 N/mm2
b) 50 N/mm2
c) 60 N/mm2
d) 100 N/mm2
23) A system of pure shear stress produces on an inclined plane
a) A tensile stress and a compressive stress
b) only tensile stresses
c) only compressive stresses
d) no direct stresses
24) Principal strains at a point are 100 x 10-6 and -200 x 10-6. What is the maximum shear strain at the point?
a) 300 x 10-6
b) 200 x 10-6
c) 150 x 10-6
d) 100 x 10-6
25) Major Principal stress at a point is 220 MPa. The radius of Mohr’s stress circle is 70 MPa. What is the minor principal stress at the point?
a) 150 MPa
b) 100 MPa
c) 80 MPa
d) 50 MPa
26) The radius of Mohr’s circle gives the value of
a) minimum normal stress
b) minimum shear stress
c) maximum normal stress
d) maximum shear stress
27) Two planes xy and yz passing through a point in a strained material. The normal and shear stresses on xy plane are +80 MPa, -30 MPa respectively and normal and shear stresses on plane yz are +30 MPa and +30 MPa respectively. What is the angle between the planes?
a) 180o
b) 135o
c) 90o
d) 45o
28) The major and minor principal stresses at a point are 120 MPa and 60 MPa respectively, on the plane passing through the point; the shear stress on the plane is 15 MPa. What is the angle of this plane with the plane of major principal stress?
a) 45o
b) 30o
c) 15o
d) 60o
29) Shear stress in a beam having triangular cross-section is maximum at
a) extreme top fibre
b) mid-depth
c) neutral axis
d) extreme bottom fibre
30) A beam with a square section of 80 mm x 80 mm is simply supported at its ends. A load W is applied at the centre of the beam. If the maximum shear stress developed in the beam section is 6 N/mm2. What is the magnitude of W ?
a) 56 k N
b) 25.6 k N
c) 51.2 k N
d) 5.12 k N