Aslide whistle is an open-closed tube with an adjustable plunger that changes the length. you are playing the slide whistle and pushing the plunger in at 8 cm/s when the tube is 15 cm long. what is the rate of change of the sound in hz/s?

df / ft = -n 12          n= 1, 3, 5, ...

Explanation:

The speed of sound is

         v = λ f

In a whistle that we approach by an open tube at one end and closed at the other, standing waves occur, which has a node in the closed part and a maximum in the open pate, whereby wavelength and the distance of the tube are related, the fundamental wave is

         λ₁ = 4L

   The harmonics are

        λ₃ = 4L / 3

        λ₅ = 4L / 5

The general formula

       λₙ = 4L / n              

with n = 1, 3, 5,…

We substitute and clear in the first equation

           f = v n / 4L                        n = 1, 3, 5,…

Let's use derivatives to find the frequency change

           df / dt = v n /4  dL⁻¹ / dt

          d / dt (1/L) = - 1 / L² dL / dt

Where dL / dt = 8 cm / s

We replace

         df / dt = - n v / L2 dL / dt

Let's calculate

         df / dt = - n 340/152 8

         df / ft = -n 12          n= 1, 3, 5, ...

electromagnetic shielding is the practice of reducing the electromagnetic field in a space by blocking the field with barriers made of conductive or magnetic materials. shielding is typically applied to enclosures to isolate electrical devices from their surroundings, and to cables to isolate wires from the environment through which the cable runs. electromagnetic shielding that blocks radio frequency electromagnetic radiation is also known as rf shielding.

the shielding can reduce the coupling of radio waves, electromagnetic fields and electrostatic fields. a conductive enclosure used to block electrostatic fields is also known as a faraday cage. the amount of reduction depends very much upon the material used, its thickness, the size of the shielded volume and the frequency of the fields of interest and the size, shape and orientation of apertures in a shield to an incident electromagnetic

from wikipedia

find the surface area of the sphere to the nearest square unit. use a calculator.

a. 254 in.2

b. 64 in.2

c. 127 in.2

d. 1,018 in.2