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Picture of an apple falling from a tree. The unit of force is the newton (N) named after Sir Isaac Newton (1642 - 1727). He observed apples falling from a tree and realised that the force produced by a falling apple is equal to its mass times the earth's gravitational pull. He established the analysis and the theory to predict forces and resulting motion.

A newton is the force which when applied to a body of mass of 1 kilogram causes an acceleration of 1 metre per second in the direction in which the force is applied.

The earth's gravitational pull is approximately 9.81 m/s2 so 1 kg will produce a force of 9.81 N. This figure is often rounded up to 10 N for ease of use.

1 kg mass produces a force of 10N.
100 kg mass produces a force of 1,000 N.
1,000 kg mass produces a force of 10 kN.

This picture contains the following scene. A bag of sugar. Below the sugar is an arrow pointing downwards which is labelled 10 N. Silhouette of a man. Below the man is an arrow pointing downwards which is labelled 100 N. Picture of a car. Below the car is an arrow pointing downwards which is labelled 10 kN.