How long would it take for a sound impulse to travel through a copper rod 25 kilometers long? the speed of copper is 3,500

0.071 sec
0.14 sec
7.1 sec
140 sec

7.1 sec

Explanation:

The speed of sound in copper is

The lenght of the rod, which is the distance the sound wave should travel, is

We know that the relationship between distance traveled, speed and time taken is:

where t is the time taken. By re-arranging the equation and using the data of the problem, we find the time the sound wave takes to travel through the rod:

frequency or wavelenth of em radiation in a vacuum

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