Auniform flat disk of mass m and radius r rotates about a horizontal axis through its center with angular speed.
(a) what is its angular momentum?
(b) a chip of mass m breaks off the edge of the disk at an instant such that the chip rises vertically above the point at which it broke off (fig. 10-29). how high above the point does it rise before starting to fall?
(c) what is the final angular speed of the broken disk?

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