The motion of any moving object can be described by its speed– time graph. Data from the graph can be used to calculate acceleration, the distance travelled and the average speed for the motion.
\(\Delta v\) (pronounced 'delta v' is the change in speed of the object.
Acceleration is measured in metres per second per second or metres per second squared \(m\, s^{-2}\).
Example
Question
A sprinter starting at \(0\,m\, s^{-1}\) in the blocks, reaches a speed of \(10\, m\, s^{-1}\) in 4 seconds. Calculate the acceleration.
\(a=\frac{\Delta v}{t}\)
\(= \frac{10}{4}\)
\(=2.5\, m\, s^{-2}\)
We sometimes refer to a moving object as having a 'constant acceleration' or a 'uniform acceleration'. A constant or uniform acceleration means that the speed of the object changes by the same amount every second.
Acceleration and force
If an object is slowing down, when the acceleration is calculated, the answer is negative.
Example
Question
A cyclist approaching a traffic light slows down from \(5\, m\, s^{-1}\) to \(0\, m\,s^{-1}\) in 10 seconds. Calculate the acceleration.
