A nut can be opened by a lever of length 0.25 m by applying a force of 80N. What should be the length
of lever, if a force of 32 N is enough to open the
nut?
[0.625m)

The turning effect is the same in both the case

τ1 = τ2  

Load × Lever arm = Load × Lever length

80 N × 0.25 × 10-2 =  32 × Lever length

Lever length = (80 N × 0.25 × 10-2) / 32

Lever length = 0.625 m = 62.5 cm

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

ingenuity says that the answer is 2.7 m.