Resultant Force

Key Stage 3

The Resultant Force is the overall force on an object.

A resultant force can be calculated by taking forces that act in opposite directions and subtracting one from the other.


There is 4N up and the 7N down. 7N - 4N = 3N. The resultant force is 3N down.	There is 4N left and the 3N right. 4N - 3N = 1N. The resultant force is 1N left.	There is 6N up and the 6N down. 6N - 6N = 0N. The resultant force up and down is 0N. There is 6N left and the 4N right. 6N - 4N = 2N. The resultant force is 2N to the left.

The resultant force is the sum of all forces acting on an object.

When forces act in the same direction their magnitudes are added together.

When forces act along the same line but in opposite directions; one is subtracted from the other.

When forces are at right angles to one another they can be added using Pythagoras theorem to find the magnitude of the resultant force and then trigonometry can be used to find the direction of the resultant force.