A female orb spider has a mass of 0.55 g . She is suspended from a tree branch by a 1.2 m length of 0.0020-mm-diameter silk. Spider silk has a density of 1300 kg/m3.
If you tap the branch and send a vibration down the thread, how long does it take to reach the spider?

Respuesta :

Answer:

[tex]t=2.08*10^{-3}seconds\\ t=2.08 milliseconds[/tex]

Explanation:

Given Data

Mass= 0.55g = 0.00055 kg

length=1.2 m

diameter=0.0020 mm

density=1300[tex]\frac{kg}{m^{3} }[/tex]

time=?

Solution

[tex]V=\sqrt{\frac{F}{u} }[/tex]

u is mass/length and F is tension

F(tension)=m*g

F=(0.00055)*(9.8)

F=[tex]5.39*10^{-3}N\\ Volume=pi*d^{2}*L\\ Volume=(3.14)*(2*10^{-6} )^{2}*(1.2)\\ Volume=1.5072*10^{-11}m^{3}[/tex]

[tex]mass=desnsity*volume\\m=1300*(1.5072*10^{-11}) \\m=1.959*10^{-8}kg\\[/tex]

Mass per length(u) is given as

[tex]u=\frac{1.959*10^{-8} }{1.2} \\u=1.6328*10^{-8}\frac{kg}{m}[/tex]

[tex]V=\sqrt{\frac{F}{u} }\\ V=\sqrt{\frac{5.39*10^{-3} }{1.6328*10^{-8} } } \\V=574.55 \frac{m}{s}[/tex]

and for 1.2m length time is

[tex]t=L/V\\t=\frac{1.2}{574.55}[/tex]

so the answer is

[tex]t=2.08*10^{-3}seconds\\ t=2.08 milliseconds[/tex]