7-4* A timber beam consists of three 50 x 200-mm planks fas tened together to form an I-beam 200 mm wide x 300 m deep, as shown in Fig. P7-4. If the flexural stress at point Ad the cross section is 7.5 MPa (T), determine a. The flexural stress at point B of the cross' section b. The flexural stress at point C of the cross section. c. The flexural stress at point D of the cross section. 200 mm 50 mm 100 mm 200 mm B 50 mm 25 mm Figure P7-4

7-4* A timber beam consists of three 50 x 200-mm planks fas tened together to form an I-beam 200 mm wide x 300 m deep, as shown in Fig. P7-4. If the flexural stress at point Ad the cross section is 7.5 MPa (T), determine a. The flexural stress at point B of the cross' section b. The flexural stress at point C of the cross section. c. The flexural stress at point D of the cross section. 200 mm 50 mm 100 mm 200 mm B 50 mm 25 mm Figure P7-4

University Physics Volume 1

18th Edition

ISBN:9781938168277

Author:William Moebs, Samuel J. Ling, Jeff Sanny

Publisher:William Moebs, Samuel J. Ling, Jeff Sanny

Chapter12: Static Equilibrium And Elasticity

Section: Chapter Questions

Problem 73AP: Two thin rods, one made of steel and the other of aluminium, are joined end to end. Each rod is 2.0m...

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What Is Static Equilibrium? Problems 13 are grouped. 1. C A ball is attached to a strong, lightweight rod (Fig. P14.1). The rod is supported by a horizontal pin near the top. The ball is at rest. Is the ball in static equilibrium? If not, why not? If so, which type of equilibrium is itstable, unstable, or neutral? Hint: What would happen if you displaced the ball slightly? FIGURE P14.1
Assume Youngs modulus for bone is 1.50 1010 N/m2. The bone breaks if stress greater than 1.50 108 N/m2 is imposed on it. (a) What is the maximum force that can be exerted on the femur bone in the leg if it has a minimum effective diameter of 2.50 cm? (b) If this much force is applied compressively, by how much does the 25.0-cm-long bone shorten?
A 100-N weight is attached to a free end of a metallic wire that hangs from the ceiling. When a second 100-N weight is added to the wire, it stretches 3.0 mm. The diameter and the length of the wire are 1.0 mm and2.0 m, respectively. What is Young’s modulus of the metal used to manufacture the wire?
Two thin rods, one made of steel and the other of aluminium, are joined end to end. Each rod is 2.0m long and has cross-sectional area 9.1mm2 . If a 10,000N tensile force is applied at each end of the combination, find: (a) stress in each rod; (b) strain in each rod; and, (c) elongation of each rod.
A uniform wire (Y = 2.0 1011 N/m2) is subjected to a longitudinal tensile stress of 4.0 107 N/m2. What is the fractional change in the length of the wire?
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
The keystone of an arch is the stone at the top (Fig. P14.9). It is supported by forces from its two neighbors, blocks A and B. Each block has mass m and approximate length L. What can you conclude about the force exerted by each block, FA and FB, for the keystone to remain in static equilibrium? That is, show that the equilibrium conditions are satisfied by the components of the forces FAx, FAy, FBx, and FBy. Assume the arch is symmetric. FIGURE P14.9
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?
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