A sled slides down a hill with friction between the sled and hill but negligible alr resistance. Which of the following must be correct about the resulting change in energy of the sled Earth system? A) The sum of the kinetic energy and the gravitational potential energy changes by an amount equal to the energy dissipated by friction,
B)The gravitational potential energy decreases and the kinetic energy is constant.
C)The decrease in the gravitational potential energy is equal to the increase in kinetic energy
D)The gravitational potential energy and the kinetic energy must both decrease.

A) The sum of the kinetic energy and the gravitational potential energy changes by an amount equal to the energy dissipated by friction,

Explanation:

it is called kinetic energy

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