# Acceleration

How fast your velocity changes. Speeding up, slowing down and turning all count as acceleration.

Physics (university) · Part 01: Motion and vectors · Card 3 of 8 · Last updated 2026-10-19

## Analogy

The gas pedal, the brake and the steering wheel all cause acceleration.

## Example

**Car pulling away**

a = change in v / time
a = (27 - 0) m/s / 9 s
a = 3 m/s^2

## In practice

A car goes from 0 to 27 m/s in 9 s. Its acceleration is 3 m/s squared.

## Practice

### Flashcards

- **What is the unit of acceleration in SI?** Metres per second squared (m/s^2).

### Interview questions

**Explain why a car going round a bend at steady speed is still accelerating.**

- Acceleration is a change in velocity
- Direction changes even if speed does not
- Acceleration points toward the centre of the bend

## Questions people ask

### Can an object have zero velocity and non-zero acceleration?

Yes. A ball thrown upward stops for an instant at its highest point, but gravity is still pulling it. Its velocity is zero there while its acceleration is still 9.8 m/s^2 downward. If acceleration were zero, the ball would stay at the top forever.

### What does negative acceleration mean?

Negative acceleration means the acceleration points in the negative direction you chose. It does not always mean slowing down. A car moving in the negative direction and speeding up has negative acceleration. Slowing down happens when velocity and acceleration point in opposite directions.

## Related concepts

- [Velocity](https://studyvisually.com/learn/science/physics-university/physics-university-part-1/physics-university-part-1-concept-2)
- [Displacement](https://studyvisually.com/learn/science/physics-university/physics-university-part-1/physics-university-part-1-concept-1)
- [Constant-acceleration equations](https://studyvisually.com/learn/science/physics-university/physics-university-part-1/physics-university-part-1-concept-4)
- [Free fall](https://studyvisually.com/learn/science/physics-university/physics-university-part-1/physics-university-part-1-concept-5)

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