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moldylime moldylime
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11 years ago Edited: 11 years ago, moldylime
Working through the online assignments. I'll post the ones I don't get. I hope you guys can help.

PB 16.48 The water molecules now in your body were once part of a molecular cloud. Only about onemillionth of the mass of a molecular cloud is in the form of water molecules, and the mass density of such a cloud is roughly 4.0×10?21

Estimate the volume of a piece of molecular cloud that has the same amount of water as your body.

a.       1.0×1029  cm^3
b     1.0×1031  cm^3
c     1.0×1033  cm^3
d     1.0×1035  cm^3
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moldylime Author
wrote...
11 years ago
Pb 16.50 Isolated molecular clouds can have a temperature as low as 12  and a particle density as great as 1.20×105 particles per cubic centimeter.

What is the minimum mass that a cloud with these properties needs in order to form a star? In solar masses
MORIGOGO
moldylime Author
wrote...
11 years ago
Pb 16.52 The Sun is essentially a gas cloud in which the forces of pressure and gravity balance each other.We can therefore use the equation in Mathematical Insight Gravity Versus Pressure in the textbook to estimate the interior temperature of the Sun from its mass and particle density.

What is the average number density of particles within the Sun, given that the average mass per particle is about  gram? in particles / cm ^3
wrote...
11 years ago
Pb 16.52 The Sun is essentially a gas cloud in which the forces of pressure and gravity balance each other.We can therefore use the equation in Mathematical Insight Gravity Versus Pressure in the textbook to estimate the interior temperature of the Sun from its mass and particle density.

What is the average number density of particles within the Sun, given that the average mass per particle is about  gram? in particles / cm ^3

One question per thread... I will help answer this one for you though Rightwards Arrow

density = mass/volume

the density of the sun is solar mass/(4/3 pi r^3) where r is the radius of he sun (the volume of a sphere is 4.3 pi r^3)

M sun=2x10^33kg
r sun = 6.96x10^10 cm

so density of sun = 2x10^33g/(4/3 pi x (6.96x10^10)^3)

density = 1.4 g/cm^3 or about 1.4 times the density of water
since each particle has a mass of 10^(-24) g, this mass density equates to a number density of

1.4 g/cm^3 x 1 particle/10^(-24g)=1.4x10^24 particles/cm^3
moldylime Author
wrote...
11 years ago
Thanks Slight Smile
wrote...
11 years ago
Thanks Slight Smile

You're welcome, are you good with the other ones?
moldylime Author
wrote...
11 years ago
No, still haven't figured them out.
ppk
wrote...
Valued Member
On Hiatus
11 years ago
Pb 16.50 Isolated molecular clouds can have a temperature as low as 12  and a particle density as great as 1.20×105 particles per cubic centimeter.

What is the minimum mass that a cloud with these properties needs in order to form a star? In solar masses

Use Jeans Mass equation...



where n is the particle number density, m is the mass of the 'average' gas particle in the cloud, T is the gas temperature, and the "k" is the Boltzmanns constant.
wrote...
11 years ago
thank you
jcs
wrote...
11 years ago
Great!
tfr
wrote...
11 years ago
This is great help and recommand to all users to look over these answers for helping them on a final exam
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