## Density

A substance's mass per unit volume.

### Unit Density

$kg/m^3$

### Formula

$\text{Density} = \frac{\text{Mass}}{\text{Volume}}$

## Mass

Measure of the amount of matter a substance contains.

### Unit Mass

$kg$

### Formula

$\text{Mass} = \text{Volume} \times \text{Density}$

## Volume

The amount of space taken up by a substance.

### Unit Volume

$m^3$

### Formula

$\text{Volume} = \frac{\text{Mass}}{\text{Density}}$

## Weights on a Balance

Two weights balanced on a beam on a pivot at its center, positioned at equal distances from the pivot, have equal mass.

$W$

If they differ in weight, the heaver weight has to be closer to the pivot. Also the weights multiplied by their distances from the fulcrum are equal.

$W$