A spring is attached to the ceiling and pulled 8 cm down from equilibrium and released. The amplitude decreases by 17% each second. The spring oscillates 19 times each second. Find an equation for the distance, D the end of the spring is below equilibrium in terms of seconds, t.

D(t) = 8(0.83)^(t) cos 38πt

Explanation:

We are told that the spring oscillates 19 times each second.

Thus, period = 1/19

We are also told that it's pulled 8cm downwards and the amplitude decreases by 17% each second.

Thus;

Amplitude;A = 8 × (1 - (17/100))^(t)

A = 8(0.83)^(t)

If we consider the function;

y = A cos (bx - c) + d

Now, 2π/b = period

So, 1/19 = 2π/b

b = 38π

So, D(t) = 8(0.83)^(t) cos (38πt - c) + d

Since we started from minimum,

Vertical shift, d = 0 and horizontal shift c = 0

So,we now have;

D(t) = 8(0.83)^(t) cos 38πt

a.metals can become magnetic if they have many spinning electrons that create magnetic fields.d.only some metals are attracted by magnets; these metals are called ferromagnetic.

d.wrapping an insulated wire around a metal with ferromagnetic properties and applying an electric current.

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