How much work, in kilojoules, went into thermal energy produced by friction?

The question is incomplete. Here is the complete question.

Suppose the mass of a loaded elevator is 1600 kg.

(a) What force, in Newtons, must be supplied by the elveator's cable to produce an acceleration of 0.745 m/s² upwards against a 185N frictional force?

(b) How much work, in joules, is done by the cable in lifting the elevator 21m?

(c) What is the final speed, in meters per second, of the elevator if it starts from rest?

(d) How much work, in kilojoules, went into thermal energy produced by friction?

(a) F = 1377 N

              (b) W = 28917 J

              (c) v = 5.6 m/s

              (d) W = 3.885 kJ

Explanation:

(a) According to Newton's Second Law: , in which, is the vetorial sum of all the forces in a system and its unit is [F] = kg.m/s² or newton (N).

In the elevator's case, and assuming going upwards is positive:

F - 185 = 1600(0.745)

F = 1377 N

For an elevator to produce an acceleration of 0.745m/s² upwards, the cables have to supply a force of 1377 newtons.

(b) Work is the energy transferred to an object while is being moved. It is calculated as: W = F.s. Its unit is [W] = N.m or Joule (J)

In the elevator's cable:

W = 1377.21

W = 28917 J

The work done by the elevator's cable is W = 28917 joules.

(c) Acceleration is variation in velocity along time. Since we know the displacement of the elevator:

where:

v₀ is initial velocity, which is this case v₀=0 because it starts from rest;

a is acceleration;

Δx is the displacement

Replacing values:

v = 5.6 m/s

Final speed of the elevator is 5.6 m/s.

(d)

W = 185(21)

W = 3885 J

Work transferred into thermal energy because of friction is W = 3.885 kJ.

force tends to be low and long diustance masses are high

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