To find the magnitude of the normal force, you must express Fn in terms of Fw since Ff is an unknown. Using the equations you found in the two previous parts, find an expression for Fn involving Fw and θ but not Ff. CosθFf - sinθFn = 0FfSinθ + FnCosθ - Fw = 0

cosθFf-sinθFn=0 (1)

 cosθFn+sinθFf-Fw=0 (2)

multiplying (1 ) by sinθ and (2) by cosθ

and substracte (2) - (1)

hence we get

∴ Fn=Fwcosθ

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

r = ρ x length / area  

ρ = r x area / length  

ρ is in ohm-meters  

in basic units, it is m³kg/s³a²  

i think this is it.