50. In a disc-type axial clutch, the friction contact takes places within an annular region with outer and inner diameters 250 mm and 50 mm, respectively. An axial force F is needed to transmit a torque by a new clutch. However, to transmit the same torque, one needs an axial force F2 when the clutch wears out. If contact pressure remains uniform during operation of a new clutch while the wear is assumed to be uniform for an old clutch, and the coefficient of friction does not change, then the ratio F/F, is (round off to 2 decimal places). 51. The truss shown in the figure has four members of length and flexural rigidity EI, and one member of length 2 and flexural rigidity 4EI. The truss is loaded by a pair of forces of magnitude P, as shown in figure. 45 l, EI l. EI e2.4EI l, EI WO The smallest value of P, at which any of the truss members will buckle is (A) (B) EI (2 2 (C) 22 EI 202 52. Bars of square and circular cross-section with 0.5m length are made of a material with shear strength of 20 MPa. The square bar cross-section dimension is 4cm x 4cm and the cylindrical bar cross-section diameter is 4cm. The specimens are loaded as shown in the figure. Tensile load Compressive load 80 kN 80 kN Torsional load Bending load 320 Nm 64 Nm Which specimens(s) will fail due to the applied load as per maximum shear stress theory? (A) Tensile and compressive load specimens (C) None of the specimens (B) Torsional load specimen (D) Bending load specimen