Forces can be measured using a force meter. Force meters contain a spring connected to a metal hook. The spring stretches when a force is applied to the hook. The bigger the force applied, the longer the spring stretches and the bigger the reading.
The unit of force is called the newton, and it has the symbol N. So 100 N is a bigger force than 5 N.
People often confuse mass and weight. Remember that weight is a force, and is measured in newtons. Mass is measured in kilograms (kg).
The mass of an object is the amount of matter or "stuff" it contains. The more matter an object contains, the greater its mass. An elephant contains more matter than a mouse, so it has a greater mass. Mass is measured in kilograms, kg, or grams, g.
A 100 kg object has a greater mass than a 5 kg object. Remember an object's mass stays the same wherever it is.
All objects have a force that attracts them towards each other. This is called gravity. Even you attract other objects to you because of gravity, but you have too little mass for the force to be very strong.
Gravitational force increases when:
the masses are bigger
the objects are closer
Gravity only becomes noticeable when there is a really massive object like a moon, planet or star. We are pulled down towards the ground because of gravity. The gravitational force pulls in the direction towards the centre of the Earth.