- #1
Freye
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Homework Statement
In outer space, the density of matter is about one atom per cm^3, mainly hydrogen atoms, and the temperature is about 3.4K. Calculate the average speed of the hydrogen atoms, and the pressure (in atmospheres)
M_H = 1.0079au = 1.67 X 10^-27 Kg
1 Hydrogen atom per cm^3 = 100 hydrogen atoms per m^3
K (Boltzmann's constant) = 1.381 X 10^-23
T = 3.4K
Homework Equations
m[tex]\bar{}v[/tex]^2 /2 = 3kT/2
PV = Nm[tex]\bar{}v[/tex]^2 /3
The Attempt at a Solution
part 1:
m[tex]\bar{}v[/tex]^2 /2 = 3kT/2
[tex]\bar{}v[/tex] = [tex]\sqrt{}3(1.381 X 10^-23)(3.4)/(1.67 X 10^-27)[/tex]
[tex]\bar{}v[/tex] [tex]\approx[/tex] 300m/s
part 2:
Consider V = 1m^3
PV = Nm[tex]\bar{}v[/tex]^2 /3
P =Nm[tex]\bar{}v[/tex]^2 /3V
=(100)(1.67 X 10^-25)(300)^2/3(1)
P [tex]\approx[/tex] 5X 10^-19 N/m^2 [tex]\approx[/tex] 5 X10^-24 atm
As usual, I get the first part of the question right, but the answer to the second part is 5 X 10^-22 not ^-24. Anyone know what I'm doing wrong?