### Video Transcript

Which of the following is used to work out acceleration? Is it distance multiplied by time, distance divided by time, speed divided by time, or speed multiplied by time?

Acceleration is the rate of change of the speed of the object. If a car accelerates for example, its speed is increasing and if it decelerates, its speed is decreasing. To be a little bit more strict in our definition, we can say that the acceleration is the change in speed of the object over a given period of time.

If we write this out, we write it as acceleration equals change in speed over time and this is the same as saying change in speed divided by time. We, therefore, use the definition speed divided by time to work out acceleration.

Another way of working this out would have been to recall the things we know about a speed-time graph. We can deduce two things from these graphs. The area under the curve or the straight line tells us the distance travelled. And the gradient of the line or the curve at a given point tells us its acceleration.

To find the gradient of this straight line, for example, we could use rise over run. The rise is the change in speed of whatever this object is. And the run is the time. Once again, we can see that it’s speed over time or speed divided by time.