**Mass** is a measure of how much matter is contained within an object. Its SI unit is the **kilogram**.

The mass of an object can be found by pushing on it with a known force *F* and dividing the size of that force by the resulting acceleration (*a*).^{[1]}

[math] m = \frac {F}{a} [/math]

Mass is different from weight (force) in that its value does not change if gravity changes. For example, on Earth, where the acceleration due to gravity is 9.8 m/s^{2}, a person who has 60 kg of mass weighs 588 Newtons (132 lbs). On the moon, where the acceleration due to gravity is about 1/6 of what it is on Earth, that same 60 kg person weighs just 98 Newtons (~22 lbs).

To read more about the SI unit of mass, the kilogram, click here.

## References

- ↑ Sears, Zemansky, and Young,
*Fifth Edition University Physics*. Addison-Wesley Publishing Company, 1979.