# Homework Help: Physics Thermal Properties HW Problem

1. Dec 3, 2013

### Eagle's Wings

1. The problem statement, all variables and given/known data

A deuteron is the nucleus of a hydrogen isotope and consists of one proton and one neutron. The
plasma of deuterons in a nuclear fusion reactor must be heated to about 300 million K.
(a) What is the RMS speed of the deuterons? Is this a significant fraction of the speed of light c =
3 x 10^8 m/s?
(b) What would the temperature of the plasma be if the deuterons had an RMS speed equal to
0.10 c?

R=8.314; T=300E6K

2. Relevant equations

v$_{rms}$=$\sqrt{\frac{3RT}{M}}$

3. The attempt at a solution

I know how to solve this, but I dont get the first part of the question. how do you find M? I tried M=1.008, but that doesnt make sense.

Last edited: Dec 3, 2013
2. Dec 3, 2013

### SteamKing

Staff Emeritus
If a deuteron has one proton and one neutron, does it make sense that M = 1.008?

After all, you can look these things up on the internet.

3. Dec 3, 2013

### Eagle's Wings

oh, thanks. I just add Mp + Mn to get M...right?