In the figure, the load P = 1 N, length L = 1 m, Young’s modulus E = 70 GPa, and the cross-section of the links is a square with dimension 10 mm $$ \times $$ 10 mm. All joints are pin joints.

The stress (in Pa) in the link AB is _______.

$$(Indicate\,\,compressive\,\,stress\,\,by\,\,a\,\,negative\,$$
$$\,sign\,\,and\,\,tensile\,\,stress\,\,by\,\,a\,\,positive\,\,sign)$$

A square plate of dimension L $$ \times $$ L is subjected to a uniform pressure load P = 250 MPa on its edges as shown in the figure. Assume plane stress conditions. The Young’s modulus E = 200 GPa.

The deformed shape is a square of dimension 𝐿 − 2$$\delta .$$ If 𝐿 = 2 m and $$\delta $$ = 0.001 m, the Poisson’s ratio of the plate material is __________ .

A horizontal bar with a constant cross-section is subjected to loading as shown in the figure. The Young’s modules for the sections AB and BC are 3E and E, respectively.
For the deflection at C to be zero, the ratio P/F is ________.

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 __________.