Resultant Forces

This lesson covers resultant forces and their effects on objects as required by the AQA GCSE Physics specification (4.5.3). When multiple forces act on an object, you can replace them with a single force that has the same overall effect — this single force is called the resultant force. Understanding resultant forces is essential for predicting whether an object will accelerate, decelerate, change direction, or remain in equilibrium.

---

What Is a Resultant Force?

The resultant force is the single force that has the same effect as all the individual forces acting on an object combined. It is sometimes called the net force or unbalanced force.

To find the resultant force, you must consider:

• The magnitude (size) of each force.
• The direction of each force.

---

Forces Along the Same Line

When forces act along the same straight line, calculating the resultant is straightforward.

Same Direction

If forces act in the same direction, you add their magnitudes.

Example: A force of 8 N to the right and a force of 5 N to the right.

Resultant = 8 N + 5 N = 13 N to the right

Opposite Directions