A wire stretched between two rigid supports vibrates in its fundamental mode with a frequency of $45 \;Hz$. The mass of the wire is $3.5 \times 10^{-2} \;kg$ and its linear mass density is $4.0 \times 10^{-2} \;kg m ^{-1} .$ What is

$(a) $ the speed of a transverse wave on the string, and

$(b)$ the tension in the string?

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Mass of the wire, $m=3.5 \times 10^{-2} \,kg$

Linear mass density, $\mu=\frac{m}{l}=4.0 \times 10^{-2} \,kg\, m ^{-1}$

Frequency of vibration, $v=45 \,Hz$

$l=\frac{m}{\mu}=\frac{3.5 \times 10^{-2}}{4.0 \times 10^{-2}}=0.875\, m$

$l-$ Iength of the wire,

The wavelength of the stationary wave ( $\lambda$ ) is related to the length of the wire by the relation:

$\lambda=\frac{2 l}{n}$

Where, $n=$ Number of nodes in the wire

For fundamental node, $n=1:$

$\lambda=2 l \Rightarrow\lambda=2 \times 0.875=1.75\, m$

The speed of the transverse wave in the string is given as:

$v=v \lambda=45 \times 1.75=78.75\, m / s$

The tension produced in the string is given by the relation:

$T=v^{2} \mu$

$=(78.75)^{2} \times 4.0 \times 10^{-2}=248.06 \,N$

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  • [JEE MAIN 2019]

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