A wire of length “Lo” and cross-sectional area S supports a weight W vertically. a) This fine wire has a Young’s modulus = E and participates in the elastic zone as if it were a very small spring of constant force. Determine the force constant of the spring b) the behavior of the wire is represented in the graph. What would be the force constant for a copper wire 75.0 cm long and 1.291 mm in diameter? c) What weight W would the wire in part b) have if it were stretched 1.25 m

Use the graph in Figure P14.46 to list the three materials from greatest Youngs modulus to smallest. Explain your reasoning. FIGURE P14.46

Review. A wire of length L, Youngs modulus Y, and cross-sectional area A is stretched elastically by an amount L. By Hookes law, the restoring force is kL. (a) Show that k = YA/L. (b) Show that the work done in stretching the wire by an amount L is W=12YA(L)2/L.

The lintel of prestressed reinforced concrete in Figure P12.27 is 1.50 m long. The concrete encloses one steel reinforcing rod with cross-sectional area 1.50 cm2. The rod joins two strong end plates. The cross-sectional area of the concrete perpendicular to the rod is 50.0 cm2. Youngs modulus for the concrete is 30.0 109 N/m2. After the concrete cures and the original tension T1 in the rod is released, the concrete is to be under compressive stress 8.00 106 N/m2. (a) By what distance will the rod compress the concrete when the original tension in the rod is released? (b) What is the new tension T2 in the rod? (c) The rod will then be how much longer than its unstressed length? (d) When the concrete was poured, the rod should have been stretched by what extension distance from its unstressed length? (e) Find the required original tension T1 in the rod. Figure P12.27