A scuba diver uses an empty vertical tube, closed at the top and open at the bottom, to measure his depth below sea level when diving in the ocean. The tube is 7.30 cm long. He dives below the surface until the water has risen into the tube a distance of 2.78 cm from the open end of the tube. Assuming the temperature of the air in the tube stays constant during the dive, what is the diver's depth at this point? The average density of sea water is 1,030 kg/m3.

the independent variable, or the one that is intentionally manipulated is the speed.

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

conservation of mass

mass before something happens = mass afterwards