Density
How much mass is packed into each unit of volume. Density = mass / volume, in kg per cubic metre (kg/m3).
Last updated
Analogy
A bag of feathers and a bag of sand are the same size, but sand has far more stuff packed in.
Example
mass = 240 kgvolume = 0.03 m3density = 240 / 0.03= 8,000 kg/m3
In practice
Objects float when they are less dense than the liquid they sit in.
Practice
Flashcards
- What is the formula for density?Density = mass / volume.
Questions people ask
Why does a steel ship float?
The ship is hollow and full of air, so its overall density, with the air included, is less than the density of water. A solid lump of steel sinks because steel is denser than water. The shape of a hull spreads the steel over a big volume.
How do you measure the density of an irregular object?
Find its mass using a balance. Find its volume by lowering it into a measuring cylinder of water and noting how far the level rises. Then divide mass by volume. A stone of 90 g that raises the water by 30 cm3 has a density of 3 g/cm3.