Pressure is a scalar (ordinary number) defined as Force over Area.
The pressure under the feet is the weight of the person divided by area in contact with the floor. The pressure under the little feet is the larger.
Pressure in a heavy fluid (air, water etc.) depends on the depth and the weight per cubic meter. Pressure 10 meters down in the sea is two atmospheres. Pressure 20 meters down is three atmospheres etc. Divers must be careful not to stay too deep for to long - otherwise nitrogen will dissolve in their blood and turn their veins to beer hoses when they surface. The condition is called the bends, and can be fatal.
Pressure is isotropic (the same in all directions) and depends only on depth. The pressure at the bottom of a meter tall yard-glass is the same as the pressure one meter down in a lake.
A really tall fish tank is difficult to make, because the bottom seal must withstand the pressure of many meters of water. For this reason no high-rise building has a fish tank the height of the stair-well. Nice idea ... but the glass at the bottom of the tank would be cm's thick if the building were many stories high.
Question: if we did make a tank the height of the Petronas towers, could goldfish swim to the bottom?
For many years air pressure at sea level was quoted as 14.7 pounds per square inch. There are still pressure gauges used in industry, and for car tires, that are calibrated in this way, but the scientific community uses the Pascal as the unit of pressure. One Pascal is a pressure of one Newton per square meter.
Air pressure at sea level is almost exactly....
The Pascal is the MKS unit of pressure. It is often convenient to quote pressure in Newtons per square cm, or in some other unit, meters of water, or cm of mercury. Mercury has a density of 13.57 g/cc. A Air pressure will support a column of mercury that is 76 cm high. Water is less dense. Air pressure is approximately 10 meters of water. At a depth of 30 meters a diver is subjected to four atmospheres.
Isobars (lines of equal pressure) are marked on weather maps in millibars. (The Bar is almost exactly one atmosphere at STP).
Questions
1 What do the numbers 14.7, 76, 100 and 100,000 have in common?
They are all measurements of air pressure in different unit systems.
2 Find the mass of the atmosphere.
2 Show that air pressure is 8000 meters of air at STP.