A roll of paper is rolled on the floor in such a way that it is leaving paper on the behind it as it rolls. The paper left behind remains stationary on the floor. The roll is given an initial velocity Vi= 3.8 m/s. The initial radius of the roll is R = 1 m. Find the velocity of the roll Vf in m/s, when the radius of the roll is r = 0.6 m. Assume the roll rolls without slipping and that gravity acts on the roll. Also assume that the mass distribution of the paper on the roll is homogeneous. (Take g = 10 m/s^2)

heats surface water 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