360_Physics ProblemsTechnical Physics

360_Physics ProblemsTechnical Physics - 362 P12.30 Static...

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362 Static Equilibrium and Elasticity P12.30 Count the wires. If they are wrapped together so that all support nearly equal stress, the number should be 20 0 100 . kN 0.200 kN = . Since cross-sectional area is proportional to diameter squared, the diameter of the cable will be 11 0 0 1 mm cm a f ~. P12.31 From the defining equation for the shear modulus, we find x as x hf SA == × ×× 500 10 200 3 0 10 14 0 10 238 10 3 64 5 .. . m N Nm m m 22 ej af e j or x 2 . m m . P12.32 The force acting on the hammer changes its momentum according to mv F t mv if += a f so F mv v t fi = . Hence, F = −− 30 0 10 0 20 0 0110 818 10 3 . . . kg m s m s s N. By Newton’s third law, this is also the magnitude of the average force exerted on the spike by the hammer during the blow. Thus, the stress in the spike is:
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