Question

An 80.0-m-long, 2.10-mm-diameter
copper wire is stretched between two
poles. A bird lands at the center point of
the wire, sending a small wave pulse out
in both directions. The pulses reflect at
the ends and arrive back at the bird’s
location 0.750 seconds after it landed.
Determine the tension in the wire.

Answer 1

An 80.0-m-long, 2.10-mm-diameter  copper wire is stretched between two  poles. A bird lands at the center point of  the wire, sending a small wave pulse out  in both directions. The pulses reflect at  the ends and arrive back at the bird’s

location 0.750 seconds after it landed. The tension in the wire is 353.11 N.

Bird is sitting at the mid point of the wire

So the wave will travel at one end of the wire and again reflect back to the position of the bird

speed of the wave is given as

$v = \frac{L/2 + L/2}{v}$

$v = \frac{80}{0.75}$

$v = 106.67 m/s$

now we know that

$v = \sqrt{\frac{T}{\rho A}}$

here we know that

$\rho = 8960 kg/m^3$

now we have

$A = \pi d^2/4$

$A = \pi(\frac{2.10 \times 10^{-3}}{2})^2$

$A = 3.46 \times 10^{-6}$

now we have

$106.67 = \sqrt{\frac{T}{8960 \times 3.46 \times 10^{-6}}}$

$T = 353.11 N$

#Learn

Topic : Speed of wave in string

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