Edexcel A Level Physics:复习笔记2.10 Mass, Weight & Gravitational Field Strength

Mass, Weight & Gravitational Field Strength


  • Mass is the measure of the amount of matter in an object
    • Consequently, this is the property of an object that resists change in motion
  • The greater the mass of a body, the smaller the change produced by an applied force
    • The SI unit for mass is the kilogram (kg)


  • Weight is the force a body experiences due to being in a gravitational field, it is given by the equation

W = mg

  • Where
    • m = mass (kg)
    • g = gravitational field strength (N kg−1)

Gravitational Field Strength

  • Gravitational field strength is the force per kilogram that acts on an object, it is found using the equation


  • Where
    • F = weight (N)
    • m = mass (kg)
  • On the Earth's surface the average gravitational field strength = 9.81 N kg−1

Constant Acceleration in Freefall

  • Freefall is used to describe falling objects where the only force is weight
    • Drag forces are ignored
    • By considering freefall we can see that all objects must fall with exactly the same value for acceleration, regardless of their mass or weight