6-2. Determine the force in each member of the truss and state if the members are in tension or compression. Set P₁=45 kN, P2 = 30 kN. P1 CY P2 D B 2 m A 1.5 m

(a) When water freezes, its volume increases by 9.05% (that is, V/V0=9.05102 ). What force per unit area is water capable of exerting on a container when it freezes? (It is acceptable to use the bulk modulus of water in this problem.) (b) Is it surprising that such forces can fracture engine blocks, boulders, and the like?

A disk between vertebrae in the spine is subjected to a shearing force of 600 N. Find its shear deformation, taking it to have the shear modulus of 1109 N /m2. The disk is equivalent to a solid cylinder 0.700 cm high and 4.00 cm in diameter.

Review. On a day that the temperature is 20.0C, a concrete walk is poured in such a way that the ends of the walk are unable to move. Take Youngs modulus for concrete to be 7.00 109 N/m2 and the compressive strength to be 2.00 109 N/m2. (a) What is the stress in the cement on a hot day of 50.0C? (b) Does the concrete fracture?

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

An aluminium (=2.7g/cm3) wire is suspended from the ceiling and hangs vertically. How long must the wire be before the stress at its upper end reaches the proportionality limit, which is 8.0107N/m2 ?

A steel cable 2.00 m in length and with cross-sectional radius 0.350 mm is used to suspend from the ceiling a 10.0-kg model aircraft that is flying in a horizontal circle with an angular speed of 6.00 rad/s. What is the strain produced in the cable?

A copper rod with length 1.4 m and cross-sectional area 2.0 cm2 is fastened to a steel rod of length L and cross-sectional area 1.0 cm2. The compound structure is pulled on each side by two forces of equal magnitude 6.00 104 N (Fig. P14.57). Find the length L of the steel rod if the elongations (L) of the two rods are equal. Use the values Ysteel = 2.0 1011 Pa and YCu = 1.1 1011 Pa. FIGURE P14.57

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.

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