A professor has to haul a cart down a ramp. The ramp has an angle of about 10 degrees and is about 5 meters long. His initial speed at the top of the ramp is 5.4 m/s, and the cart has a mass of about 100 kg. How hard does he have to pull on the cart so that at the bottom of the ramp, its speed does not exceed 6.4 m/s

power out to power in less than 100%

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