516 Sound WavesP17.55vdt=2: dvt==×=212650 101856013...msskmejafP17.56(a)The speed of a compression wave in a bar isvY×=×ρ20 0 107860504 10103..Nmkg m23.(b)The signal to stop passes between layers of atoms as a sound wave, reaching the back end ofthe bar in timetLv×−0800159 104..m5.04 10 m ss3.(c)As described by Newton’s first law, the rearmost layer of steel has continued to moveforward with its original speed vifor this time, compressing the bar by∆Lvti×=×=−−12 01 59 101 90 101 9043..smmmbg.(d)The strain in the rod is: ∆LL=×−−190 10238 1033..m0.800 m.(e)The stress in the rod is:σ=FHGIKJ×=−YLL∆20 0 102 38 10476103MPa2ej.Since >400 MPa , the rod will be permanently distorted.(f)We go through the same steps as in parts (a) through (e), but use algebraic expressionsrather than numbers:The speed of sound in the rod is vY=.The back end of the rod continues to move forward at speed vi
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