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- Thread starter The Exestentialist
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In summary, to find the atmospheric pressure, you need the mass of the atmosphere and the surface area of the planet. If you only have the percentages of each gas, it will not help you find the pressure. The equation for finding the pressure is to divide the weight of the atmosphere by the surface area of the planet. It is important to check the units and make sure to multiply by the acceleration due to gravity.

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You need the mass of the atmosphere.

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By composition, I meant quantity of each gas.DrStupid said:You need the mass of the atmosphere.

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If you know the total mass of each gas separately then you know the total mass of all the gasses put together.The Exestentialist said:By composition, I meant quantity of each gas.

If you know only the percentages (by weight) then what you know will not help you find the pressure you seek.

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In what units? I tried this with Earth's atmosphere and I didn't get the right answer.Chestermiller said:

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What units did you use for the weight of the Earth's atmosphere and the surface area of the planet and what answer did you get?The Exestentialist said:In what units? I tried this with Earth's atmosphere and I didn't get the right answer.

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I used 5.1x10jbriggs444 said:What units did you use for the weight of the Earth's atmosphere and the surface area of the planet and what answer did you get?

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Check your arithmetic and check your figure for theThe Exestentialist said:I used 5.1x10^{18}kg for the atmosphere's weight and 4*π*12,742,000^{2}m^{2}for the surface area of the Earth. I got 2,499,684 kg/m^{2}

Edit: 7 significant figures of computed output on an input that is only stated to 2 digits reflects more precision than is justified.

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Radius. Sigh. I hate when I make stupid mistakes like that. Thank you all for your help.

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PaThe Exestentialist said:In what units? I tried this with Earth's atmosphere and I didn't get the right answer.

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Don't forget to multiply by g.jbriggs444 said:Check your arithmetic and check your figure for theradiusof the Earth in meters. I get around 11,000 kg/m^{2}on the back of an envelope.

Edit: 7 significant figures of computed output on an input that is only stated to 2 digits reflects more precision than is justified.

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I was assuming kilograms-force, but yes, I agree.Chestermiller said:Don't forget to multiply by g.

Atmospheric pressure is the force per unit area exerted by the weight of Earth's atmosphere above a given point.

Atmospheric pressure is commonly measured using a barometer, which measures the height of a column of mercury or other liquid in a tube.

The SI unit for atmospheric pressure is pascal (Pa), but it is often measured in other units such as millibar (mb) or inches of mercury (inHg).

As altitude increases, atmospheric pressure decreases. This is because there is less air above a given point at higher altitudes, resulting in lower pressure.

Atmospheric pressure can be calculated using the ideal gas law, which relates pressure, volume, temperature, and the number of gas molecules. It can also be calculated using weather data such as temperature and altitude.

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