• Forces are in the form of either a push or a pull.

• Since forces have direction, they are vector quantities. (see Speed or Velocity)

• We measure forces in newtons N.

Weight

This is an example of a force, since the weight of an object acts towards the centre of the Earth.

Friction

This is a force which opposes motion. Without the force of friction between two surfaces, we would slide when we tried to walk.

Newton’s Third Law                                                                              

This states that every force (ACTION) has an equal and opposite force (REACTION).

Look at the following site : Internet site link

Archimedes Principle

When an object is weighed in air and then partially or totally immersed in a liquid :

This first site is rather amusing : Internet site link

This second site is more scientifically informative: Internet site link

Since a force is a vector, we represent it by a line with an arrowhead.

e.g. A weight of 10 N

The length of the line, including the arrowhead, represents the size of the force F. So, if a scale of 1cm representing 2 N, was used, the vector, including the arrowhead would be 5cm long.

e.g. An object is on a table : 

F is the weight of the object (ACTION) and F1 is the REACTION

Since the forces are vectors :

N.B.  Both F and F1 are drawn from the centre of mass of the object. (see Centre of Mass)

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