A hypothetical engineering stress-strain curve shown in the figure has three straight lines PQ, QR, RS with coordinates P(0,0), Q(0.2,100), R(0.6,140) and S(0.8,130). 'Q' is the yield point, 'R' is the UTS point and 'S' the fracture point.

The tougness of the material (in MJ/m³) is __________.

The figure shows cross-section of a beam subjected to bending. The area moment of inertia (in mm⁴) of this cross-section about its base is __________.

A simply-supported beam of length $$3L$$ is subjected to the loading shown in the figure.

It is given that $$P = 1$$ $$N,$$ $$L = 1$$ $$m$$ and Young’s modulus $$E = 200$$ $$GP$$a. The cross-section is a square with dimension $$100$$ $$mm$$. The bending stress (in Pa) at the point A located at the top surface of the beam at a distance of $$1.5L$$ from the left end is _____________ .

(Indicate compressive stress by a negative sign and tensile stress by a positive sign).

The spring constant of a helical compression spring DOES NOT depend on