# Molecule Kinetics: Calculating Temperature from Speed Upon Moon Re-Entry

• bpw91284

## Homework Statement

A space vehicle returning from the Moon enters Earth’s atmosphere at a speed of about 4.9E4 km/h. Molecules (assum nitrogen) striking the nose of the vehicle with this speed correspond to what temperature?

KE=0.5mv^2=kT
k: constant

## The Attempt at a Solution

I'm lost.

Look up the mass of an N2 molecule and Boltzmann's constant, k, put them into your first equation and solve for T. ?

Look up the mass of an N2 molecule and Boltzmann's constant, k, put them into your first equation and solve for T. ?

Can't look up mass, only molecular weight. Where mass=#mols*molecular weight.

Can't look up mass, only molecular weight. Where mass=#mols*molecular weight.

You can so look up the mass of a single nitrogen atom. It's in the periodic table in atomic mass units. What's an atomic mass unit in kilograms? Can also be looked up.

You can so look up the mass of a single nitrogen atom. It's in the periodic table in atomic mass units. What's an atomic mass unit in kilograms? Can also be looked up.

N=14.00674u
1 u ≈ 1.66053886 × 10−27 kg

Then just solve for T with 0.5mv^2=kT?

Thanks,
Brandon

Except remember the question says 'molecules' and nitrogen is N2 (two nitrogen atoms).

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