# Acceleration

#### Back to Physics Grade 9/10

## Description

This is a simple physics tutorial aimed at high school students in grades 9 and 10 (GCSE, HSC) exploring the concept of acceleration. The video tutorial will be up shortly.

## What is acceleration?

We’ve learned that velocity is a measurement of the *speed* and *direction* of an object. If *either* the speed *or* the direction in which an object is moving changes, there is a *change in its velocity*. For example:

- When an object goes from rest to movement, its speed changes; thus its velocity does too.
- Similarly when it slows down, its speed changes; thus its velocity does too.
- Lastly, when an object changes its direction (e.g. by turning a corner), its velocity changes too.

All three of these changes in velocity are a form of *acceleration*. That is, acceleration is a measure of the change in velocity over time.

Broken down, the formula is this:

It can also be expressed like this:

where:

*a*= acceleration (measured in metres per second squared, m/s^{2})*u*= initial velocity (measured in metres per second, m/s)*v*= final velocity (measured in metres per second, m/s)*ti*= initial time (measured in seconds, s)*tf*= final time (measured in seconds, s)

## Why does acceleration occur?

Acceleration occurs as a result of *unbalanced forces*, but don't worry about that for now; you'll learn all about it in future tutorials.

## Is acceleration a vector or a scalar measurement?

We know that velocity is a vector measurement. Consequently, acceleration is too. This means that it has *both* magnitude and direction.

## What unit do we use for acceleration?

The most commonly used unit for acceleration in physics tutorials is meters per second squared (*m/s ^{2}*) (which is also used in the GCSE), however it could be any distance measurement divided by any time measurement squared. For example, it could be reported as kilometers per hour squared (

*km/hr*), or miles per hour squared (

^{2}*mi/hr*).

^{2}