Uniform velocity
The table below gives the displacement of an object travelling in one direction, measured from its starting point.
| Time t (s) | 0 | 1 | 2 | 3 | 4 |
|---|---|---|---|---|---|
| Displacement s (m) | 0 | 3 | 6 | 9 | 12 |
In every second the displacement increases by 3 m. So this motion is taking place at a constant velocity, also called a uniform velocity.
What constant velocity means
For an object moving at constant velocity, neither the magnitude nor the direction of the velocity changes.
So a car going round a roundabout at a steady speed is not moving at constant velocity — its direction keeps changing.
Finding the displacement
If an object travels along a straight path at a constant velocity of 6 m s−1, its displacement changes by 6 m every second, and the direction of the motion stays the same.
Travelling for 5 seconds
displacement = 6 m s−1 × 5 s = 30 m
The formula to remember
displacement = velocity × time
This is just "velocity = displacement ÷ time" rearranged. Remember either one and you can build the other.