1. In the lecture, the key idea about elasticity is that many solid objects behave like a spring when stressed. Just like solid objects, realistic springs do not obey Hooke's law forever. If pulled on hard enough, they reach a point of permanent deformation. Ultimate strength Yield strength Stress (F/A) 0 Rupture Range of permanent deformation Linear (elastic) range Strain (AL/L) We noted that Hooke's law for a force due to a spring F₁(x) = −k(x − xo) where xo is the equilibrium position of the spring, is a conservative force. Is the realistic spring force (one that looks like the figure above) a conser- vative force? Explain.

A steel specimen of 12 mm diameter extends by 6.31 x 10-2 mm over a gauge length of 150 mm when subjected to an axial load of 10 kN. The same specimen undergoes a twist of 0.5° an a length of 150 mm over a twisting moment of 10 N-m. Using the above data, determine the elastic constants E, Mu, G and K.

Solve Clearly!!!!z,

QUESTION 3 UWE The figure below shows the cross section of unsymmetric Bristol I-beam. The I-beam experiences a maximum M=4 kNm sagging bending moment. And the beam is pulled apart with end-loading forces of 20 kN. Calculate the maximum tensile stress the beam experiences. (State your answer to the nearest whole number Mega-Pascals.) 120 mm 60 mm I 40 mm 30 mm 220 mm 30 mm