# Resultant force

The single force that has the same effect as all the forces on an object added together, taking direction into account.

Physics (school) · Part 02: Forces and Newton's laws · Card 2 of 8 · Last updated 2026-10-19

## Analogy

A tug of war: the winning side's extra pull is what decides the result.

## Example

**Tug of war**

Left team pulls 500 N.
Right team pulls 450 N.
Resultant = 500 - 450
= 50 N to the left

## In practice

If the resultant is zero, the forces are balanced and the object keeps doing what it was doing.

## Practice

### Flashcards

- **What is true about the forces at terminal velocity?** They are balanced: drag equals weight, so the resultant is zero.

### Interview questions

**A car of mass 800 kg has an engine force of 2,400 N and 400 N of drag. Find its acceleration.**

- Resultant force = 2,400 - 400 = 2,000 N
- Use F = ma, so a = F / m
- a = 2,000 / 800 = 2.5 m/s squared

## Questions people ask

### How do you work out a resultant force?

Add forces that point the same way, and subtract forces that point opposite ways. Then state the direction of the bigger one. A 500 N pull to the left and a 450 N pull to the right leave a resultant of 50 N to the left.

### What does a zero resultant force mean?

The forces are balanced. The object either stays still or keeps moving at the same speed in a straight line. A car on a flat road at a steady 20 m/s has its driving force exactly balanced by drag and friction, so it does not speed up or slow down.

## Related concepts

- [Newton's second law](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-4)
- [Terminal velocity](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-8)
- [Force](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-1)
- [Newton's first law](https://studyvisually.com/learn/science/physics-school/physics-school-part-2/physics-school-part-2-concept-3)

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