At the surface of the Earth, the value of gravitational field strength, g, is approximately 10N/kg. More precisely, this is 9.81N/kg, but it is fine to use 10N/kg up to GCSE level.

The amount of weight an object has is determined by how much mass it has and the gravitational field strength. The higher the gravitational field strength, the higher the weight.

Key points:

• Weight changes based on the mass
• g is always the same on Earth (9.81N/kg)
• you get different g values on different planets and moons

The value of the gravitational field strength, g, decreases as you get further away from the planet. You need to travel a very long way up for it to be significantly different.