The top of a tin can is removed and the empty can is inverted over a pair of billiard balls on a table, as shown in figure 5. for certain combinations of sizes and weights, the configuration shown is stable, but for other combinations, the can tips over when released. it is proposed to set up a demonstration for a temperance lecture by using in sequence a frozen-orange-juice can and a beer can with the same pair of billiard balls. investigate whether tipping will occur for the following sizes and weights: diameter of ball weight of ball diameter of can weight of can with lid removed 0.57 n assume that all the contacts are frictionless orange juice beer 45 mm 2.0n 70 mm 1.0n 45 mm 2.0n 50 mm figure 5

1/0.14nm = 10^10/1.4 a lot

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