The force of gravity (weight)
All objects with massThe amount of matter an object contains. Mass is measured in kilograms (kg) or grams (g). produce a gravitational field. The more mass an object has, the greater its gravitational field will be.
Planet size and gravitational field strength
Weight is the force acting on an object due to gravity - it has the unit newtons (N) and acts towards the centre of a gravitational field. The weight of an object can be measured using a calibrated spring-balance, often called a Newton meter.
Weight is a non-contact forcesThe push or pull acting between objects that are not physically touching when they interact. because gravity exerts its force through a field. An object does not need to be touching the Earth to have a weight.
Space, the Moon landing and different planets are used to discuss gravity
Gravitational field strength (g) is measured in newtons per kilogram (N/kg). The Earth's gravitational field strength is 9.8 N/kg. This means that for each kg of mass, an object will experience 9.8 N of force.
Where there is a weaker gravitational field, the weight of an object is smaller. For example, the gravitational field strength of the Moon is 1.6 N/kg. This means that for each kg of mass, an object will experience 1.6 N of force. Therefore, an astronaut will weigh less on the Moon than they do on the Earth.
