Lesson 4 of 7

Balanced and unbalanced forces

Goal: Explain what balanced and unbalanced forces do to motion.

Puzzles for this lesson

The forces on an object combine into one overall force, called the resultant force.

Opposite directions: subtract. 500 N one way and 300 N the other leave a resultant of 200 N, the way the bigger force acts.
Same direction: add. 500 N and 300 N the same way make 800 N.
Balanced forces on an object are equal and opposite. The resultant is zero, and the object is in equilibrium.
Unbalanced forces leave a resultant, which changes the speed or direction of the object.

Your turn

This lesson’s activity starts here in a moment.

I can work out the resultant of forces in a line.I can say whether an object is in equilibrium.

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Force A push or a pull

Resultant force The single force left when forces are combined

Balanced forces Equal and opposite forces on one object

Unbalanced forces Forces that do not cancel out

Equilibrium When the forces on an object are balanced

For teachers: AQA 3.1.1, 3.1.3 · Pearson Edexcel 41.1, 41.2, 41.3 · Cambridge 8Pf.03