Physics

6.2 - Acceleration

6 min

The acceleration equation

Deceleration and uniform acceleration

Acceleration and distanceOutside your course

note 1 of 3

What acceleration is

Acceleration is how quickly velocity is changing - the change in velocity in a certain amount of time.
A change in velocity can be a change in speed, a change in direction, or both.
Acceleration is a vector, so it can be positive or negative.
Deceleration is negative acceleration: when something slows down, the change in velocity is negative.

note 2 of 3

The formula for acceleration

$a = \frac{v - u}{t}$

Where:

$a$ = Acceleration, in metres per second squared (m/s²)
$v$ = Final velocity, in metres per second (m/s)
$u$ = Initial velocity, in metres per second (m/s)
$t$ = Time taken, in seconds (s)

The change in velocity is the final velocity minus the initial velocity ( $v - u$ ).

note 3 of 3

Worked example - Time for a given acceleration

A cyclist accelerates at 1.5 m/s² from 3.0 m/s to 7.5 m/s. Find the time it takes to do this.

Step 1 - Rearrange the acceleration equation for time

$t = \frac{v - u}{a}$

Step 2 - Substitution and calculation

$t = \frac{7.5 - 3.0}{1.5} = 3.0 s$

key terms

TermDefinition

AccelerationThe rate of change of velocity, equal to the change in velocity divided by the time taken.

DecelerationNegative acceleration, which happens when an object slows down.

end of notes

Key points to remember

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6.3 - Distance-Time GraphsNext up