Mass, Weight and Gravity

• Gravity is the Force of Attraction between all masses.
• Gravity effects


  On the surface of a planet, it makes all things accelerate towards the ground.
• Gravity effects


  It gives everything a weight.
• Gravity effects

  It keeps planets, moons and satellites in their orbits. The orbit is a balance between the forward motion of the object and the force of gravity pulling it inwards.
• Mass is the amount of 'stuff' in an object.

  For any given object this will have the same value anywhere in the universe.
• Weight is caused by the pull of gravity. In most questions the weight of an object is just the force of gravity pulling it towards the centre of the Earth.
• An object has the same mass whether it's on Earth or on the Moon - but its weight will be different.

  A 1 kg mass will weigh less on the Moon than it does on Earth, simply because the force of gravity is pulling on it is less.
• Weight is a force measured in newtons. It's measured using a spring balance or a newton meter.

  Mass is not a force. It's measured in kilograms with a mass balance.
• Weight = mass x gravitational field strength