Gravity is the universal force of attraction acting between all matter. Gravity one of the weakest forces we know yet all objects with mass-produce a gravitational field. The greater the mass, the greater the gravitational field strength is.
Gravitational field strength is measured in Newton's per kilogram (N/Kg). The gravitational field strength on earth is 9.8 N/Kg which means that every kilogram of mass on earth will experience 9.8 Newtons of force.
The gravitational field strength is different on different planets, for example on the moon it is only 1.6 N/Kg so when astronauts went to the moon they experienced 1.6 Newtons of force per kilogram which means they weighed less on the moon than they did on the earth.
To calculate the weight of an object you use the equation
weight = mass x gravity.
For example a 60 kg person on earth would have a weight of __