The Lagoon Nebula ( Fig. E18.24 ) is a cloud of hydrogen gas located 3900 light-years from the earth. The cloud is about 45 light-years in diameter and glows because of its high temperature of 7500 K. (The gas is raised to this temperature by the stars that lie within the nebula.) The cloud is also very thin; there are only 80 molecules per cubic centimeter. (a) Find the gas pressure (in atmospheres) in the Lagoon Nebula. Compare it to the laboratory pressure referred to in Exercise 18.23. (b) Science-fiction films sometimes show starships being buffeted by turbulence as they fly through gas clouds such as the Lagoon Nebula. Does this seem realistic? Why or why not? Figure E18.24
The Lagoon Nebula ( Fig. E18.24 ) is a cloud of hydrogen gas located 3900 light-years from the earth. The cloud is about 45 light-years in diameter and glows because of its high temperature of 7500 K. (The gas is raised to this temperature by the stars that lie within the nebula.) The cloud is also very thin; there are only 80 molecules per cubic centimeter. (a) Find the gas pressure (in atmospheres) in the Lagoon Nebula. Compare it to the laboratory pressure referred to in Exercise 18.23. (b) Science-fiction films sometimes show starships being buffeted by turbulence as they fly through gas clouds such as the Lagoon Nebula. Does this seem realistic? Why or why not? Figure E18.24
The Lagoon Nebula (Fig. E18.24) is a cloud of hydrogen gas located 3900 light-years from the earth. The cloud is about 45 light-years in diameter and glows because of its high temperature of 7500 K. (The gas is raised to this temperature by the stars that lie within the nebula.) The cloud is also very thin; there are only 80 molecules per cubic centimeter. (a) Find the gas pressure (in atmospheres) in the Lagoon Nebula. Compare it to the laboratory pressure referred to in Exercise 18.23. (b) Science-fiction films sometimes show starships being buffeted by turbulence as they fly through gas clouds such as the Lagoon Nebula. Does this seem realistic? Why or why not?
A cylinder of diameter S, of height h, contains pure gas with equation
PV = nRT at constant temperature T_0. The z axis is directed upwards
and the gravitational field is assumed to be uniform.
1) Using the fundamental principle of hydrostatic statistics, show that
dp = -pgdz where p = p (z) is the gas pressure at height z.
2) If P_0 is the gas pressure at the foot of the pole, calculate the
pressure p (z) at height z.
3) In the case of wind (M = 29 g / mol: R = 8.31J/ mol.k) at
temperature T_0 = 300K, calculate the height of the poles necessary
to observe the change in pressure (pressure at the threshold) at 5% .
10
Imagine that you have air in a sealed glass container that has a volume of 1 liter. The pressure inside the container is 1013 hPa and the temperature is 20◦C. You now inject cloud droplets into the chamber without letting any air leak out. The droplets have a radius of 10 micrometers, and you inject a concentration of drops that is typical of what you find in a cloud (200 drops per cm3). Will there be a change in the gas pressure? If so, by what amount? Please provide a calculation. What does your answer tell you about the presence of particles in the atmosphere and their potential influence on pressure?
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