The ratio of the length and diameter of a simply supported uniform circular beam which experiences maximum bending stress equal to tensile stress due to same load at its mid span, is

If a solid shaft (diameter 20 cm, length 400 cm, N = 0.8 x 10^{5} N/mm^{2}) when subjected to a twisting moment, produces maximum shear stress of 50 N/mm^{2}, the angle of twist in radians, is

The maximum B.M. due to an isolated load in a three hinged parabolic arch, (span l, rise h) having one of its hinges at the crown, occurs on either side of the crown at a distance