An object has uniform acceleration if the acceleration is constant throughout the journey. Therefore the speed is always changing at the same rate. Be careful – the speed is never constant, because there is always acceleration.

If there is uniform acceleration, we can calculate the acceleration using the following equation:

Where:

• final velocity, $v$, in metres per second, m/s
• initial velocity, $u$, in metres per second, m/s
• acceleration, $a$, in metres per second squared, m/s²
• distance, $s$, in metres, m

When using the equations of uniformly accelerated motion:

• take care with signs; use + and – for vector quantities such as velocity and acceleration that are in opposite directions
• remember that s represents displacement; this is not the same as the distance travelled if the object has changed direction during the motion.

To work out the distance travelled by an object that changes direction, calculate the displacement both before and after the change in direction, and add these together