Wave Motion 3 Question 10

10. A steel wire of length 1m, mass 0.1kg and uniform cross-sectional area 106m2 is rigidly fixed at both ends. The temperature of the wire is lowered by 20C. If transverse waves are set-up by plucking the string in the middle, calculate the frequency of the fundamental mode of vibration.

Given : Ysteel =2×1011N/m2,

(1984,6M)

αsteel =1.21×105/C

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Answer:

Correct Answer: 10. 11Hz

Solution:

  1. The temperature stress is σ=YαΔθ or tension in the steel wire T=σA=YAαΔθ Substituting the values, we have

T=(2×1011)(106)(1.21×105)(20)=48.4N

Speed of transverse wave on the wire, v=Tμ

Here, μ= mass per unit length of wire =0.1kg/m

v=48.40.1=22m/s

Fundamental frequency

fo=v2l=222×1=11Hz



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