Ball a of mass m is connected to one end of a massless stick
with length `, the other end of which is connected to a pivot.
the stick is held vertically above the pivot and is then given
an infinitesimal kick. it swings down, and at the bottom of its
motion it collides elastically with ball b, also of mass m, which
hangs from a string with length ` and which is initially at rest.
ball b picks up whatever speed ball a had and then swings
upward in circular motion.
(a) a what point does ball b leave its circular motion and enter
freefall projectile motion?
(b) how high does ball b go in the resulting projectile motion

it takes about 30 days for it to break down

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