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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, please someone help, this micro macro stuff is stupid... I am not sure about the vrms formula is correct, since in the book it says its for molecules, but i can't find anything on atoms... I am pretty sure i have done something wrong for the number density, as i don't know, coz its in atoms/cm^3... and I am just stuck please some help me...