Velocity
- The velocity of a moving object is similar to its speed, except it also describes the object’s direction
- The speed of an object only contains a magnitude - it’s a scalar quantity
- The velocity of an object contains both magnitude and direction, e.g. ‘15 m/s south’ or ‘250 mph on a bearing of 030°’
- Velocity is therefore a vector quantity because it describes both magnitude and direction
The cars in the diagram above have the same speed (a scalar quantity) but different velocities (a vector quantity). Fear not, they are in different lanes!
In my experience of teaching GCSE students, confusion can often arise around the idea of the directional component of velocity. In real life, the direction would be left, right, forward, backward etc., but in calculations, direction is just represented by positive and negative values. The positive direction is usually forwards for the object moving. If two objects are moving in different directions, or one object that moves in different directions, it doesn't actually matter which you define as positive as long as the opposing direction is negative. Once students realise this, I find that they understand velocity much better.
