1.3 Mass Weight, 1.4 Density

• Mass


  A measure of the quantity of matter in an object
• Weight


  The gravitational force on an object that has mass
• Weight

  Unit: newton (N)
• Mass


  Unit: kilogram (kg)
• Gravitational field strength


  9.8 N/kg
• Calculate the weight of a 65 kg person

  1. W = mg

  2. W = 65 kg * 9.8 N/kg

  3. W = 637 N
• Find the mass of an object that weighs 490 N


  1. W = mg

  2. m = W/g

  3. m = 490 N / 9.8 N/kg

  4. m = 50 kg
• 35 kg or 330 N

  330 N is heavier
• 1 kg of steel and 1 kg of feathers have the same mass, but so much feathers are needed to balance a tiny piece of steel
• Density


  Mass per unit volume
• Find the density of a 256 g cube with side length 2 cm


  1. V = s^3

  2. V = (2 cm)^3 = 8 cm^3

  3. ρ = m/V

  4. ρ = 256 g / 8 cm^3

  5. ρ = 32 g/cm^3
• Find the volume of 0.5 kg of seawater with density 1.030 g/cm^3

  1. ρ = m/V

  2. V = m/ρ

  3. V = 0.5 kg / (1.030 g/cm^3)

  4. V = 485 cm^3
• Find the mass of 0.25 m^3 of mercury with density 13600 kg/m^3

  1. ρ = m/V

  2. m = ρ*V

  3. m = 13600 kg/m^3 * 0.25 m^3

  4. m = 3400 kg
• Calculate the density of the liquid

  ρ = 0.8 g/cm^3