Consider the situation shown in figure. The wire which has a mass of 4.00 g oscillates in its second harmonic and sets the air column in the tube into vibrations in its fundamental mode. Assuming that the speed of sound in air is `40 m s^-1`, find the tension in the wire.
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Answer

A

Explanation

Let `n_0=`frequency of the tuning fork,
`T=`Tension of the string
`L=40cm=0.4m, m=4g`
`=4xx10^-3kg`
`So, m=Mass/(Unit Length)=10^-2kg/m`
`n_0=1/(2L) sqrt(T/m)`
So, `2nd Harmonic 2n_0=(2/(2L))sqrt(T/m)`
As it is tension with fundamental frequency of vibration in the air column.
`rarr 2n_0=340/4xx1=85Hz`
`rarr 85=2/(2xx0.4)sqrt(T/14)`
`=T=(85)^2xx(0.4)^2`
`=11.6Newton`