Resultant Forces

This lesson covers resultant forces and their effect on objects, as required by AQA GCSE Combined Science Trilogy (8464), section 6.5.1. The resultant force is one of the most important concepts in the entire Forces topic — it determines whether an object accelerates, decelerates, or remains at constant velocity.

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What Is a Resultant Force?

A resultant force is the single force that has the same effect as all the individual forces acting on an object combined. It is the overall (net) force.

• If forces act in the same direction, add them.
• If forces act in opposite directions, subtract the smaller from the larger.
• The resultant acts in the direction of the larger force (when forces are opposite).

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Calculating Resultant Forces Along a Line

Same Direction

Two forces of 6 N and 4 N both act to the right:

Resultant = 6 + 4 = 10 N to the right

Opposite Directions

A force of 12 N acts to the right and 5 N acts to the left:

Resultant = 12 − 5 = 7 N to the right