Laura and Elana are discussing how to solve the following problem: "A canary sits 10 m from the end of a 30-m-long clothesline, and a grackle sits 5 m from the other end. The rope is pulled by two poles that each exert a 200-N force on it. The mass per unit length is 0.10 kg/m. At what frequency must you vibrate the line in order to dislodge the grackle while allowing the canary to sit undisturbed?"

Respuesta :

Answer:

[tex]f=2.236\ Hz[/tex]

Explanation:

Given:

Length of a rope,[tex]l=30\ m[/tex]

Position of Canary on the rope from one end, [tex]l_c=10\ m[/tex]

Position of Grackle on the rope from another end, [tex]l_g=5\ m[/tex]

Tension in the rope, [tex]F_T=200\ N[/tex]

linear mass distribution on the rope, [tex]\mu=0.1\ kg.m^{-1}[/tex]

We have for the speed of wave on the string:

[tex]v^2=\frac{F_T}{\mu}[/tex]

[tex]v^2=\frac{200}{\0.1}[/tex]

[tex]v=44.7\ m.s^{-1}[/tex]

For canary to be undisturbed we need a node at this location.

Also, at the end close to Canary there must be a node to avoid any change in pattern of vibration.

So,

the distance between Canary and the closer end must be equal to half the wavelength.

[tex]\frac{\lambda}{2} =10\ m[/tex]

[tex]\Rightarrow \lambda=20\ m[/tex]

∴Wavelength of wave to be produced = 20 m. This will give us nodes at the multiples of 10 and anti-nodes at the multiples of 5.

Now, frequency:

[tex]f=\frac{v}{\lambda}[/tex]

[tex]f=\frac{44.7}{20}[/tex]

[tex]f=2.236\ Hz[/tex]