A force is a push or pull that acts on an object due to the interaction with another object. All forces between objects are either: • contact forces – the objects are physically touching • non-contact forces – the objects are physically separated. • Examples of contact forces include friction, air resistance, tension and normal contact force. • Examples of non-contact forces are gravitational force, electrostatic force and magnetic force. • Force is a vector quantity. • Students should be able to describe the interaction between pairs of objects which produce a force on each object. The forces to be represented as vectors.