Two coconuts fall freely from rest at the same time, one twice as high as the other. if the coconut from the shorter tree takes 2.0 s to reach the ground, how long will it take the other coconut to reach the ground?

Take the first coconut's starting position to be the origin, and the downward direction to be positive. The first coconut's position is determined by

where is the acceleration due to gravity.

So if it takes 2.0 s to reach the ground, then

(rounding to 2 significant digits)

The second coconut starts 20 m higher than the first, so its initial displacement is -20 m relative to the origin, and its overall position over time is given by

Reaching the ground is a matter of obtaining , which requires a time of

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