Speed, Density & Pressure

Speed, Density & Pressurevideo

Speed, density & pressure

What are speed, density and pressure?

• Speed, density and pressure are frequently used compound measures

  • Speed is equal to distance divided by time

  • Density is equal to mass divided by volume

  • Pressure is equal to force divided by area

What should I know about speed, distance and time?

• Speed is commonly measured in metres per second (m/s) or kilometres per hour (km/h)

  • The units indicate speed is distance per time
    $\mathrm{Speed}=\frac{\mathrm{Distance}}{\mathrm{Time}}$

• 'Speed' (in this formula) means 'average speed'

• In harder problems there are often two journeys or two parts to one longer journey

What should I know about density, mass and volume?

• Density is usually measured in grams per centimetre cubed (g/cm³) or kilograms per metre cubed (kg/m³)

  • The units indicate that density is mass per volume
    $\mathrm{Density}=\frac{\mathrm{Mass}}{\mathrm{Volume}}$

• You may need to use a volume formula to find the volume of an object first

What should I know about pressure, force and area?

• Pressure is usually measured in Newtons per square metre (N/m²)

  • The units of pressure are often called Pascals (Pa) rather than N/m²

  • The units indicate that pressure is force per area
    $\mathrm{Pressure}=\frac{\mathrm{Force}}{\mathrm{Area}}$

• Remember that weight is a force

  • It is different to mass