Many mountain roads are built so that they spiral around the mountain rather than go straight up toward the peak. discuss this design from the viewpoint of energy and power.

So, the mountain roads takes us from the base of the mountain to the top. Lets call this height h. We know that the potential energy will be:

and this equation its independent from the road we take. But, an spiral road will be longer than an direct road. This means that, if we wanna to cover at constant speed v, the time it will takes us will be longer.

As power its the rate of change of the energy over time, this means that we will need more power for the straight up road.

For any motor the amount of power we can obtain its limited, so its more convenient for our vehicles (and for ourselves) to build the roads on spiral, instead of going straight up.

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