Physics: 3

• Mass


  Quantity of matter in an object at rest relative to the observer
• Mass


  • Measured using: Kilogram (kg) and gram (g)
  • Scalar quantity

  
• Weight


  Gravitational force on an object that has mass
• Weight


  • Commonly used unit: Newton (N)
  • Vector quantity
  • Direction of weight is downward, i.e., towards the centre of the Earth
• Gravitational field


  Region of space in which a mass exerts a force of attraction on another mass
• Weight of an object


  Effect of a gravitational field on a mass
• Gravitational field strength, g

  The weight of an object depends on the strength of the gravitational force acting on it
• Mass measurement


  Electronic balances measure weight, but they are calibrated to give readings for mass

  
• Instruments for measuring mass

  • Electronic balance
  • Simple beam balance
• Density


  Ratio of mass to volume of a substance

  
• Floating and sinking


  • Substances that float on a liquid have lower densities than the liquid
  • Substances that sink in a liquid have higher densities than the liquid

  
• Ice cubes placed in three different liquids


  • The density of the liquid determines whether the ice cube floats or sinks