Balanced Forces (Edexcel GCSE Physics): Revision Note

Balanced Forces

Higher Tier Only

• A resultant force is a single force that describes all of the forces operating on a body

• When many forces are applied to an object they can be combined (added) to produce one final force which describes the combined action of all of the forces

• This single resultant force determines:

  • The direction in which the object will move as a result of all of the forces

  • The magnitude of the final force experienced by the object

• The resultant force is sometimes called the net force

• Forces can combine to produce

  • Balanced forces

  • Unbalanced forces

• Balanced forces mean that the forces have combined in such a way that they cancel each other out and no resultant force acts on the body

  • For example, the weight of a book on a desk is balanced by the normal force of the desk

  • As a result, no resultant force is experienced by the book, the book and the table are equal and balanced

A book resting on a table is an example of balanced forces

• Unbalanced forces mean that the forces have combined in such a way that they do not cancel out completely and there is a resultant force on the object

  • For example, imagine two people playing a game of tug-of-war, working against each other on opposite sides of the rope

  • If person A pulls with 80 N to the left and person B pulls with 100 N to the right, these forces do not cancel each other out completely

  • Since person B pulled with more force than person A the forces will be unbalanced and the rope will experience a resultant force of 20 N to the right

A tug-of-war is an example of when forces can become unbalanced