Weight and mass · Year 10
Mass is the amount of matter in an object, measured in kilograms; it is the same everywhere. Weight is the force of gravity on that mass, measured in newtons, and it depends on where you are. On Earth each kilogram is pulled with about 9.8 N.
Key facts
- W = mg: weight (N) = mass (kg) × gravitational field strength (N/kg).
- On Earth g = 9.8 N/kg; on the Moon about 1.6 N/kg; on Mars about 3.7 N/kg.
- Mass is measured with a balance; weight with a newton meter (spring balance).
- Mass does not change from place to place; weight does.
- Weight acts from the centre of mass, straight down towards the centre of the planet.