Units of Density and Pressure

# Units of Density and Pressure

GCSE(F), GCSE(H),

Density is the mass of a substance that occupies a given volume.

density = frac(text(mass))(text(volume)), or D = frac(M)(V)

Density is normally measured using units of g/cm3 for smaller amounts, and kg/m3 for larger amounts.

Calculations of density can be represented by a triangle:

To work out the mass, calculate density x volume: to work out density, it is mass ÷ volume, and for volume it is mass ÷ density.

Pressure is a force acting on an area. A force pressing down on a point will exert more pressure than the same force acting over a wide area. Force is measured in Newtons (shown as N) and the area is normally given in square metres.

The formula is Pressure = frac(text(Force))((Area)), or P = frac(F)(A) and is shown as N/m2, or Nm-2

The formula can also be represented by a triangle:

## Examples

1. A pair of stiletto heels occupy an area of 2cm2. What is the pressure being applied to a floor if the weight of the woman wearing the stilettos is 560N?