5.6.2 Speed

Distance

• Tells us how far an object moves (a scalar quantity).

Displacement

• The distance and direction in which an object moves in a straight line from the starting point to the finishing point (vector quantity).

Speed

• Tells us the distance an object travels in a given time (a scalar quantity).

$$\text{Speed (v)} = \frac{\text{distance (s)}}{\text{time (t)}}$$

Factors Affecting Speed

• Age – as we get older, our fitness levels will decrease and we find it harder to run at the same speed as we did before.
• Terrain – a rough terrain will have more friction, reducing speed. Similarly, if the incline is higher, it takes more energy to run at the same pace.
• Distance travelled – as distances increase, our muscles get tired and lactic acid builds up due to anaerobic respiration. This leads to muscle cramps, and we find it harder to run as fast.
• Fitness – the more fit you are, the better you are able to cope with intense exercise. This is especially true for running.