An alien floating around near alpha centauri pushes a small rock with a force of 15 n towards our solar system. if the rock is accelerating at 7 m/s squared, what would the mass of the rock be?

We're almost positive that Newton's laws of motion are true near Alpha Centauri, just as much as they're true here in OUR neighborhood.  So we can use Newton's 2nd law, and assume that

Force = (mass) x (acceleration).

(15 N) = (mass) x (7 m/s²)

We're also confident that elementary algebra works out there too, so we can divide each side of this equation by  (7 m/s²).  Then it says ...

Mass = (15 N) / (7 m/s²)

Mass = (15/7) (N-s²/m)

Mass = 2.143 kg

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