Work and energy a 68 kg students runs up a flight of stairs 3.5 meters high in 11.4 seconds. the student takes 8.5 seconds to run up the same flight of stairs during a second trial. determine the following: a. the work done in each trial. you should identify these values as w1 and w2. b. the power exerted by the student in each trial. you should identify these values as p1 and p2.

a) ,

The work done by the student in each trial is equal to the gravitational potential energy gained by the student:

where

m = 68 kg is the mass of the student

g = 9.8 m/s^2 is the acceleration of gravity

is the gain in height of the student

For the first student, , so the work done is

The second student runs up to the same height (3.5 m), so the work done by the second student is the same:

2) ,

The power exerted by each student is given by

where

W is the work done

t is the time taken

For the first student, and , so the power exerted is

For the second student, and , so the power exerted is

continuous conducting path for current, power supply

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