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Newton's first law

A body remains at rest or in a state of uniform motion unless the forces acting on it are unbalanced.
An object will stay still or carry on moving exactly the way it was unless an unbalanced force acts on it.

An apple hanging from a tree or a skydiver falling at their terminal velocity are also both examples of Newton’s First Law.

In the case of the apple the force of gravity downwards balances the force of the stalk upwards and so there is no unbalanced force acting on the apple – it therefore stays where it is.

The skydiver is falling but because the force of gravity is balanced by the drag of the air there is once again no unbalanced force and the motion of the skydiver is unchanged. This does not mean that they stop in mid air – it means that they fall at a steady speed.

© Keith Gibbs 2009