# Question #9235b

Oct 4, 2017

Mass is the quantity of being. Weight is force.

#### Explanation:

This is a basic but very important concept in science.

$\textcolor{red}{\text{Mass}}$ means the absolute quantity of an object and its SI unit is $\textcolor{red}{\text{kilogram}} \left(k g\right)$.

In contrast, $\textcolor{b l u e}{\text{weight}}$ refers to the force of gravity.
It is measured in $\textcolor{b l u e}{\text{Newton}} \left(N\right)$ On the earth, an object whose mass is $m \left(k g\right)$ has $m g \left(N\right)$ weight. ($g$ is a gravity constant: $g$ = 9.8…($m {s}^{-} 2$))

The figure is cited from "質量と重さの違い" by f_master.
http://1st.geocities.jp/f_master001/physics/htmlfile/molarity_and_gravity.html
The Japanese above says that the resistance against acceleration is mass and the gravity force is weight.

Mass of the object does not change no matter where it is put.
Weight of the object is dependent on the place.

For example, assume that I have an object X. Mass of X is $1.0 k g$.
If I were to take it to the moon, where the gravity is about one-sixth times of that of the earth, $\textcolor{red}{\text{mass of object X}}$
$\textcolor{red}{\text{would be exactly the same as that of on the earth.}}$ (i.e. $1.0 k g$)

However, $\textcolor{b l u e}{\text{the weight object X feels on the moon}}$ would be one-sixth of that on the earth. The weight is $1.0 \left(k g\right) \cdot 9.8 \left(m {s}^{-} 2\right) = 9.8 \left(N\right)$ on the earth and $9.8 \cdot \frac{1}{6} = 1.6 \left(N\right)$ on the moon.