Forces in Static Situations/Lesson Document: Difference between revisions

A force can rise in two ways:

(a) Through contact with another object. Examples:

(b) ‘Mysterious’ forces

These are non-contact forces that occur when objects interact gravitationally or magnetically. There are also ‘mysterious’ electrical no-contact forces.

It is quite legitimate to refer to these ‘non-contact’ forces as ‘mysterious’, since even scientists find it difficult to explain how they arise.

"'How do you describe a force?"'

A force is described in terms of two qualities: its size and its direction. Scientists often use an arrow to indicate the size and direction of a force:

'''Where do forces act?'''

The force of reaction acts over a whole surface of contact – it is usually drawn at the centre of the surface, slightly displaced from other ‘force arrows’ for clarity. The two surfaces are also drawn slightly apart for the same reason.

'''Balanced forces'''

A stationary object remains still because all the forces acting upon it are ‘balanced’, i.e. the effect of each force acting on a body is cancelled out by an equal and opposite force. When the forces on an object are balanced, a scientist would say there is no net force or no resultant force acting on it i.e. all the forces cancel each other out.