gravity

• gravity is the force of attraction between two objects with mass.
• the mass of an object is a scalar measure of how much matter the object is made up of. mass is measured in kilograms.
• the weight of an object is a vector measure of how gravity is acting on the mass. weight is measured in newtons.
• weight (N) = mass (kg) x gravitational field strength (N/kg)
• an object's centre of mass is the point at which the weight of the object is considered to be acting. it does not necessarily occur at the centre of the object.
• the mass of an object and its weight are directly proportional. as the mass is increased, so is the weight. weight is measured using a spring balance (or newton metre).