Two metal balls are the same size but one weighs twice as much as the other. the balls are dropped from the roof of a single story building at the same instant of time. the time it takes the balls to reach the ground below will be:

a. about half as long for the heavier ball as for the lighter one.
b. about half as long for the lighter ball as for the heavier one.
c. about the same for both balls.
d. considerably less for the heavier ball, but not necessarily half as long.
e. considerably less for the lighter ball, but not necessarily half as long.

E. considerably less for the lighter ball, but not necessarily half as long.

Explanation:

Since both metal are falling under the effect of gravity and against the air (since air resistance is not negligible), the lighter metal tends to overcome the air resistance easily due to its light weight compare to the heavy metal as such the lighter object will tend to reach the ground first before the heavier metal but not necessarily reaching the ground faster as twice the time it will take the heavier ball because the time it will take them to reach the ground is not based on the weight of the objects but the how the metals tend to resist the air easily.

the displacement produced by the body.  

the amount of force subjected to the body.  

the angle between the direction of force and displacement

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