# Reduced mass to atomic mass units conversion help please

• B
• TheCelt
In summary, the conversation is about understanding how to convert the reduced mass into atomic mass units. The equation for reduced mass is $m_1m_2/(m_1+m_2)$ and for two similar masses, it becomes $m^2 / 2m = 1/2 * m$. To convert to atomic mass units, the book uses the value of 1/2u, which is obtained by substituting the mass of 4u for $m_4$ in the equation.

#### TheCelt

Hello

I am trying to understand how to write the reduced mass into atomic mass units but i am confused how it was done.

The equation is

$$m_1m_2/(m_1+m_2)$$

For two similar masses in my particular case i have:

$$m^2 / 2m = 1/2 * m$$

Then to convert to atomic mass units, the book says it gives:

But how did they get that value? I had $$1/2 * u$$My conversion must be failing me, i am not sure how they got that value..

So the book has ##m_4 = 4u## while you have ##m_4 = u## ?

Hard to tell which is which on PF since ##m_4## hasn't been introduced here. Is it described somehow in the book ?

@BvU it was representing a $$_2^4 He$$

Don't know how to write it inline with my sentence, anyway it does seem I forgot that it would be 4u.

BvU
All clear ! (the subscript 4 was a giveaway )

Inline ##\LaTeX## by enclosing it in double #: ##\LaTeX##