258_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

258_Mechanics SolutionInstructors_Sol.Manual-Mechanics_Materials_7e.book_Gere_light.1

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Unformatted text preview: Sec_3.3.qxd 252 9/27/08 1:27 PM Page 252 CHAPTER 3 Torsion Circular Bars and Tubes P Problem 3.3-1 A prospector uses a hand-powered winch (see figure) to raise a bucket of ore in his mine shaft. The axle of the winch is a steel rod of diameter d 0.625 in. Also, the distance from the center of the axle to the center of the lifting rope is b 4.0 in. If the weight of the loaded bucket is W 100 lb, what is the maximum shear stress in the axle due to torsion? d W b W Solution 3.3-1 Hand-powered winch d 0.625 in. MAXIMUM SHEAR STRESS IN THE AXLE b 4.0 in. From Eq. (3-12): W 100 lb tmax Torque T applied to the axle: T Wb 400 lb-in. tmax tmax 16T pd3 (16)(400 lb-in.) p(0.625 in.)3 8,340 psi ; Problem 3.3-2 When drilling a hole in a table leg, a furniture maker uses a hand-operated drill (see figure) with a bit of diameter d 4.0 mm. (a) If the resisting torque supplied by the table leg is equal to 0.3 N m, what is the maximum shear stress in the drill bit? (b) If the shear modulus of elasticity of the steel is G 75 GPa, what is the rate of twist of the drill bit (degrees per meter)? d ...
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