Gravity & Weight (Edexcel GCSE Physics): Revision Note

Gravity on Different Planets

• The strength of gravity on different planets after an object's weight on that planet

• Weight is defined as:

  The force acting on an object due to gravitational attraction

• Planets have strong gravitational fields

  • Hence, they attract nearby masses with a strong gravitational force

• Because of weight:

  • Objects stay firmly on the ground

  • Objects will always fall to the ground

  • Satellites are kept in orbit

Objects are attracted towards the centre of the Earth due to its gravitational field strength

• Both the weight of any body and the value of the gravitational field strength g differs between the surface of the Earth and the surface of other bodies in space, including the Moon because of the planet or moon's mass

  • The greater the mass of the planet then the greater its gravitational field strength

  • A higher gravitational field strength means a larger attractive force towards the centre of that planet or moon

• The gravitational field strength (g) on the Earth is approximately 10 N/kg

• The gravitational field strength on the surface of the Moon is less than on the Earth

  • This means it would be easier to lift a mass on the surface of the Moon than on the Earth

• The gravitational field strength on the surface of the gas giants (eg. Jupiter and Saturn) is more than on the Earth

  • This means it would be harder to lift a mass on the gas giants than on the Earth

Value for g on the different objects in the Solar System

• On such planets such as Jupiter, an object’s mass remains the same at all points in space

• However, their weight will be a lot greater meaning for example, a human will be unable to fully stand up

A person’s weight on Jupiter would be so large a human would be unable to fully stand up