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## Homework Statement

What is the mean free path of an N

_{2}molecule in an ultra-high-vacuum chamber at a pressure of 10

^{-10}mbar?

## Homework Equations

λ=1/(√2)nσ

number density n, collision cross-section σ

p=nkT

pressure p, temperature T

σ=πd

^{2}

d molecular diameter

## The Attempt at a Solution

λ=kT/(√2)πpd

^{2}

where we know p and I can estimate d to be around 10

^{-10}m. However I am not given T, and I don't really see how I could know what it is...