Density
Forces in Action - OCR A-Level Physics
Key Definition
Density
Mass per unit volume. It is a property of the material, not the object. SI unit: $kg m^{-3}$.
Mass per unit volume. It is a property of the material, not the object. SI unit: $kg m^{-3}$.
$$\rho = \frac{m}{V}$$
- Common densities: water = 1000 $kg m^{-3}$, air = 1.2 $kg m^{-3}$, steel = 7800 $kg m^{-3}$, aluminium = 2700 $kg m^{-3}$
- Remember to convert units: 1 $cm^{3} =$ $1 \times 10^{-6}$ $m^{3}$; 1 litre = $1 \times 10^{-3}$ $m^{3}$
- An object floats if its average densityMass per unit volume of a material. Measured in kg m⁻³. is less than the densityMass per unit volume of a material. Measured in kg m⁻³. of the fluid it is in