weight, mass and gravity

• Gravity


  One of the most important forces in the universe
• Weight


  The force acting on an object due to the pull of gravity from a massive object like a planet. The force acts towards the centre of the planet and is measured in newtons (N).
• Centre of mass


  The point representing the mean position of the matter in a body. Depending on the object's shape, its centre of mass can be inside or outside it.
• Weight and mass


  Directly proportional. For a given gravitational field strength, the greater the mass of the object, the greater its weight.
• Calculating weight


  weight = mass × gravitational field strength
• Weight (W) is measured in newtons (N)
• Mass (m) is measured in kilograms (kg)
• Gravitational field strength (g) is measured in newtons per kilogram (N/kg)
• Example


  • An apple has a mass of 100 g. Calculate its weight on Earth (g = 9.8 N/kg).
• Weight = mass × gravitational field strength
• Weight = 0.1 kg × 9.8 N/kg
• Weight = 0.98 N
• Calculating weight of a 30 kg dog (g = 9.8 N/kg)

  1. Weight = mass × gravitational field strength

  2. Weight = 30 kg × 9.8 N/kg

  3. Weight = 294 N
• Gravity


  One of the most important forces in the universe
• Weight


  The force acting on an object due to the pull of gravity from a massive object like a planet
• Centre of mass


  The point representing the mean position of the matter in a body
• Weight of an object

  Directly proportional to its mass
• Calculating weight


  Weight = mass × gravitational field strength
• Weight calculation example


  • Apple with mass 100 g, weight on Earth = 0.98 N
• The weight of a 30 kg dog on Earth (g = 9.8 N/kg) is 294 N