An empty elevator weighing 100 kgs, stops at the third -level of a building and got 3 passengers weighing 200 kgs. Considering a single cable supporting the elevator cart, what is the (a) tension of the cable if it is going up at an acceleration of 1m/s2.
(b) tension of the cable if it is going down with the same acceleration of 1m/s.

Explanation:

in order for the cable to not break the tension force on the cable must be equal to the weight it supports . apparent weight of the 3 passengers plus the elevator itself must be equal to the tension force. mathematicaly:

Total apparent weight = Tension force

(a) tension of the cable if it is going up at an acceleration of 1m/s2

elevator App weight=m(a + g)

elevator App weight=100kg(10m/s2 + 1m/s2)

elevator App weight=1100N

pass. App weight=m(a + g)

pass. App weight=200kg(10m/s2)+ 1m/s2)

pass. App weight=2200N

tension F= total apparent weight

tension F=2200N+1100N

tension F=3300N

(b) tension of the cable if it is going down with the same acceleration of 1m/s.

in this case ,due to the downward movement of the elevator the acceleration is assigned a negative sign(-1m/s2)

elevator App weight=m(a + g)

elevator App weight=100kg(10m/s2 +( - 1m/s2))

elevator App weight=900N

pass. App weight=m(a + g)

pass. App weight=200kg(10m/s2)+(- 1m/s2))

pass. App weight=1800N

tension F= total apparent weight

tension F=1800N+900N

tension F=2700N

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