You have a summer job at a laboratory associated with the oversight of the Global Positioning System (GPS). The space-based part of the system consists of about three dozen satellites. Just before the summer, a new GPS satellite was launched but, due to a rocket-engine failure, it did not achieve its proper near-circular orbit around the Earth. It now moves in an elliptical orbit with its apogee at 2.65 ✕ 104 km, which is the radius of the circular orbit of a correctly positioned GPS satellite, and its perigee at 6.70 ✕ 103 km. Your boss wonders if the satellite can still be used in some way. Normal GPS satellites appear over the same point on the Earth about twice a day. Your boss asks you to calculate (a) how many times a day the satellite reaches its perigee and to determine (b) if the perigee point is regularly over a fixed point on the Earth's surface.

oh shi sorry I wish I could help but I'm stupid

nec chapter 5 contains

c. information on special occupancy areas

nec chapter 6 covers

a. special equipment

which of the following rules contain the words shall or shall not and must be adhered to?

b. mandatory rules

which of the following rules identify actions that are allowed but not required and typically cover options or alternative methods?

c. optional rules

which of the following serves as the introduction to the nec and provides an overview of the book?

a. nec article 90

organizations that test products for safety are

c. nrtls

the nec is published by the

a national fire protection association

the nec is divided into

b. 9 chapters

the nec provides informative annexes for

c. informational materials and examples

two terms from nec article 100 that trainees should become familiar with are

b. labeled and listed

explanation:

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