A uniform metal bar 100cm long balances at 20cm mark when a mass of 1.5kg is attached at 0cm mark calculate the weight of the bar (Take g=10N/kg)

30 N

Explanation:

there are two forces act on the bar:

- weight of 1.5 kg mass, w = mg = 15 N

- weight of the bar, wb

for balance,

w * Lw = wb * Lwb

Lw = length of bar from the mass to the pivot

Lwb = lenght of bar from the center of the bar to the pivot

15 * 20 = wb * (50-20)

300 = wb * 30

wb = 300/30 = 30 N

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