gravity, weight and gpe

• Gravity


  A force of attraction between two objects, with the size of the force depending on the mass of the objects and the distance between them
• For small objects like apples or buildings, the gravitational force of attraction is tiny because they have relatively low masses
• For very large objects that are far away like Jupiter, the gravitational force is also tiny because the distance is so far
• For very large objects that are close by, such as the Earth or the Moon, gravity is felt more strongly and has a big influence over nearby objects
• Gravitational field


  The field of influence around an object
• Gravitational field strength


  The strength of the gravitational field, denoted by the letter g
• The gravitational field strength on Earth is around 9.8 Newtons per kilogram
• The gravitational field strength on the Moon is 1.6 Newtons per kilogram, because the Moon is a lot smaller than the Earth
• Weight


  The force of attraction experienced by an object in a gravitational field
• Calculating an object's weight

  Take the object's mass and multiply it by the gravitational field strength
• In everyday language, we say we "weigh" 60 kilograms, not that we have a mass of 60 kilograms
• Mass is an intrinsic property of an object, while weight is the force acting on it in a gravitational field
• Gravitational potential energy


  The energy required to lift an object against the force of gravity
• Calculating gravitational potential energy


  Ep = m x g x h, where Ep is gravitational potential energy, m is mass, g is gravitational field strength, and h is height
• Gravitational potential energy is measured in Joules, as it is a form of energy
• Gravitational potential energy


  The energy stored in an object due to its position above the Earth's surface, due to the force of gravity acting on the object