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## Homework Statement

in space far from stars is filled with a very low density of hydrogen atoms, the number density is about 1atom/cm^3 and T is about 3degreeK

a. estimate the pressure in space, answer in Pa and atm.

b. what is the rms speed of the atoms

c. what is the edge length L of an LxLxL cube of gas with 1J of thermal energy

k=1.38x106-23

1atm=101.3kPa

atomic mass of hydrogen=1.67x10^-27kg

## Homework Equations

N/V=n

vrms=sqrt(3kT/m)

N/V*M=m

PV=NkT

## The Attempt at a Solution

a. P=(N/V)kT=(1/1x10-6)*1.38x10^-23*3=4.14x10^-17Pa=4x10^-22atm?

b.m=(N/V)M=(1/1x10^-6)1.67x10^-27=1.67x10^-22kg

so vrms=sqrt(9*1.38x10^-23/1.67x10^-22)=.86m/s????

and c. i have no idea, plz someone help, this micro macro stuff is stupid.... im not sure about the vrms formula is correct, since in the book it says its for molecules, but i cant find anything on atoms... im pretty sure i have done something wrong for the number density, as i dont know, coz its in atoms/cm^3.... and im just stuck plz some help me...