11-1ELASTICITY ANDPERIODICMOTION11Answers to Multiple-Choice Problems1.A2.B3.B4.A5.C6.C7.A, C, D8.B9.C10.C11.B12.C13.B14.D15.CSolutions to Problems11.1.Set Up:with The force applied to the end of the wire isandSolve: (a)(b)(c)Reflect:Our result for Yis about the same size as the values in Table 11.1. In SI units the stress is very large. Thestrain is dimensionless and small, so Yis very large and has the same units (Pa) as stress.11.2.Set Up:Solve:11.3.Set Up:The cross-sectional area of the post is The force applied tothe end of the post is The Young’s modulus of steel isSolve: (a)(b)The minus sign indicates that the length decreases.(c)11.4.SetUp:Forsteel,Theforceappliedtotheendofthelowerwireis The force applied to the end of the upper wire is Tensilestrain5Dll05F'AY.15.0 kg110.0 kg219.80 m/s225147.0 N.98.0 N.110.0 kg219.80 m/s225Y52.031011Pa.Dl5l01strain
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