# Acceleration

How quickly velocity changes. Acceleration = change in velocity / time, measured in m/s squared.

Physics (school) · Part 01: Motion and measurement · Card 6 of 8 · Last updated 2026-10-19

## Analogy

Pressing the accelerator and watching the speedometer climb every second.

## Example

**Car pulling away**

start 0 m/s, end 20 m/s
time = 8 s
a = (20 - 0) / 8
a = 2.5 m/s squared

## In practice

A negative acceleration (deceleration) is a car slowing down when the brakes go on.

## Practice

### Flashcards

- **What is the formula for acceleration?** Acceleration = change in velocity / time, in m/s squared.

### Interview questions

**A train speeds up steadily from 5 m/s to 25 m/s in 10 s. Calculate its acceleration and the distance it covers in that time.**

- Acceleration = (25 - 5) / 10 = 2 m/s squared
- Average velocity = (5 + 25) / 2 = 15 m/s
- Distance = 15 x 10 = 150 m
- Give units with each answer

## Questions people ask

### What does an acceleration of 2 m/s squared mean?

It means the velocity goes up by 2 m/s every second. If you start at rest, you are moving at 2 m/s after one second, 4 m/s after two seconds, and 6 m/s after three. The unit m/s squared is just 'metres per second, per second'.

### Is slowing down also acceleration?

Yes. Physicists use acceleration for any change in velocity, including slowing down. Slowing down gives a negative acceleration, sometimes called deceleration. A car braking from 30 m/s to 10 m/s in 4 s has an acceleration of -5 m/s squared.

## Related concepts

- [Velocity-time graph](https://studyvisually.com/learn/science/physics-school/physics-school-part-1/physics-school-part-1-concept-7)
- [Speed](https://studyvisually.com/learn/science/physics-school/physics-school-part-1/physics-school-part-1-concept-3)
- [Velocity](https://studyvisually.com/learn/science/physics-school/physics-school-part-1/physics-school-part-1-concept-4)
- [Distance-time graph](https://studyvisually.com/learn/science/physics-school/physics-school-part-1/physics-school-part-1-concept-5)

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