What Is the RMS Speed of Deuterons in a Fusion Reactor?

[Eagle's Wings]

Homework Statement

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

Homework Equations

v_{rms}=\sqrt{\frac{3RT}{M}}

The Attempt at a Solution

I know how to solve this, but I don't get the first part of the question. how do you find M? I tried M=1.008, but that doesn't make sense.

 

[SteamKing]

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.

 

[Eagle's Wings]

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