normal atmospheric pressure at sea level AT 273 kelvin is ?
Answers
1.01325 bar
The Standard Atmospheric Pressure is defined at sea-level at 273oK (0oC) and is 1.01325 bar or 101325 Pa (absolute). The temperature of 293oK (20oC) is sometimes used.
Answer:
Atmospheric pressure at sea level is approximately 100,000 pascals (101,325 Pa by definition.) Air pressure is usually measured in hectopascals (hPa), the hecto prefix corrsponding to 100 (a hecatre is a square with 100m sides), so 1 atmosphere is approximately 1000 hPa
A pascal is the SI unit for pressure, defined as 1 newton per square metre.
Earth's gravitational acceleration on the surface is approximately 10 m/s^2, so atmospheric pressure is roughly equivalent to 10,000 kg, or 10 tonnes per square metre!
Because water is about 1000 kg per cubic metre, you would need 10 cubic metres of water over 1 square metre to be equivalent to one atmosphere, which would be about 10m deep (10.34m more precisely). You can change the width and length to anything you want, but as long as you keep the depth the same, the force per unit area (the pressure) will stay the same. This means that if you dive down 10m in water, you are experiencing 1 extra atmosphere of pressure. This is also why it is physically impossible to suck water up a straw longer than 10m. As you remove the air from the straw, the pressure of the atmosphere pushes the water up to fill the partial vacuum. as you suck more air out, the vacuum gets stronger until there is no air left, and the water reaches a height of 10.3m. because there is no more air to remove, there is no way to raise the water any more without adding more pressure at the bottom.
This is the basis of a pressure gauge. If you create a high tube, and remove all the air at the top, the water will be pushed up to a certain point by the atmospheric pressure. If you change the pressure at the bottom, the level of the water wil change. If a low pressure storm goes over, there is less pressure pushing the water up the tube, so the water level will drop. If a nice high passes over, there will be more pressure, so the water level will rise.
It is possible to do this with any liquid, and it is preferable to use a more dense liquid for convenience, because 10m is fairly large! Mercury is about 13.5 times as dense as water, so you would only need 1/13.5 times the depth to create the same pressure. This is about 760mm, or 30 inches. This is where the term 'inches of mercury' comes from.