physics

• Density


  Mass per unit volume
• SI units


  • Volume: cubic metre (m^3)
  • 1 cubic metre = 1m x 1m x 1m
  • 1 cubic metre (1m^3) = 1000 litres (l)
  • 1 litre = 1000 cubic centimetres (cm^3) = 1000 millilitres (ml)
  • 1 cubic centimetre (cm^3) = 1 millilitre (ml)
• Aluminium is less dense than lead for the same volume
• Density equation


  Density = Mass / Volume
• Substance densities


  • Wood: 0.75 g/cm^3
  • Ice: 0.92 g/cm^3
  • Water: 1.00 g/cm^3
  • Aluminium: 2.70 g/cm^3
  • Copper: 8.90 g/cm^3
  • Lead: 11.4 g/cm^3
• A solid object with a density lower than that of water will float
• A battleship made of aluminium should not sink
• Calculating density


  1. Density = Mass / Volume

  2. Density = m / V

  3. V = m / ρ

  4. m = V * ρ
• Density calculations


  • Density of a block of steel with mass 9,360g and volume 1,200cm^3 is 7.8 g/cm^3
  • Mass of a block of gold with density 19.3 g/cm^3 and volume 540 cm^3 is 10,422g
  • Volume of a block of ice with density 0.92 g/cm^3 and mass 12,462g is 13,546cm^3
• Measuring volume of a liquid

  Use a measuring cylinder and read off the level on the scale
• Measuring volume of a regular solid


  Calculate volume = length x width x height
• Measuring volume of a cylinder

  Volume = π x radius^2 x height
• Measuring volume of an irregular solid

  1. Volume = Volume after - Volume before

  2. Use a Eureka (displacement) can and measure the displaced liquid
• Density calculation for an irregular solid

  • Mass of irregular solid = 350g
  • Volume of irregular solid = 80cm^3
  • Density = 350 / 80 = 4.375 g/cm^3