# Understanding mass units

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I am enrolled in a course related with physics, and we have a table of equivalencies of units to get the right units of frequencies.

Code:
    Stiffness   Mass        Frequency
kgf/m       kgf.s^2/m   rad/s

I have always work with the third row, but I want to understand the conversion between mass units only; for example to convert mass from kg to kgf.s2/m. What I have to do it?

I have always a problem for this: if I have 50kgf, so to get the mass value for this force, I have to divide by gravity, and I have kgf-s2/m. Furthermore, if I want to convert first to Newtons, then, I have to multiply by 9.80N, and finally divide by gravity to get the mass, and the value of mass is 50kg, different from the other calculation. What have I done wrong?

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## Answers and Replies

mfb
Mentor
This seems to be the mass multiplied by the gravitational acceleration g. You don't need that.
The US units have this weird mass/weight confusion where "pound" can be both, the metric system does not.

gmax137
gmax137