2. Biologists think that some spiders "tune" strands of their web to give enhanced response at frequencies corresponding to those at which desirable prey might struggle. Orb spider web silk has a typical diameter of 20 μm, and spider silk has a density of 1300 kg/m3. To have a fundamental frequency at 100 Hz, to what tension must a spider adjust a 12-cm-long strand of silk?

Respuesta :

Answer: 2.35*10^-4 N

Explanation:

The linear mass density is

μ = m / L

Recall, ρ = m / V, so that, m = ρV

Substitute this in the equation

μ = ρV / L

Also, recall, V = AL. Substituting this in the equation, we have

μ = ρAL / L = ρA

Again, recall, A = πr², so that

μ = ρπr²

μ = 1300 * 3.142 * [10*10^-6]²

μ = 4.085*10^-7 kg/m

the wavelength of the wave in the silk, λ = 2L

λ = 2 * 0.12 = 0.24 m

The wave speed, v = fλ

v = 100 * 0.24 = 24 m/s

v = √(T / μ)

v² = T / μ

T = v²μ

T = 24² * 4.085*10^-7

T = 2.35*10^-4 N

Answer:

The tension is 2.35x10⁻⁴N

Explanation:

Given:

d = 20 μm = 20x10⁻⁶ m

L = 12 cm = 0.12 m

f = 100 Hz

The transverse velocity is:

[tex]v=\sqrt{\frac{T_{s} }{\mu } }[/tex] (eq. 1)

Where

Ts = web´s tension

μ = linear mass density

The linear mass density is:

[tex]\mu =\frac{\pi d^{2}\rho }{4}[/tex] (eq. 2)

Where

ρ = density of the spider silk = 1300 kg/m³

The fundamental frequency is:

[tex]f=\frac{v}{2L}[/tex]

Replacing eq. 1 and 2 and clearing the tension Ts:

[tex]f=\frac{1}{2L} \sqrt{\frac{4T_{s} }{\pi d^{2}\rho } } \\T_{s} =\pi d^{2} f^{2} L^{2} \rho[/tex]

[tex]T_{s} =\pi *(20x10^{-6} )^{2}*(100 )^{2} *(0.12 )^{2}*1300=2.35x10^{-4} N[/tex]