Abox of mass 13kg sits on a table with a coefficient of static friction of 0.85. what is the maximum force of static friction?

108.3 N

Explanation:

The maximum force of static friction acting on the box is given by:

where

is the coefficient of static friction

N is the normal reaction of the table on the box

Since the box is in equilibrium along the vertical direction, the normal reaction N is equal to the weight of the box, so:

And so, the maximum force of static friction is

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

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