Graphs are a good way of showing motion visually. The two types of graphs which are of most interest are distance/time graphs and speed/time (or velocity/time) graphs. Graphs are particularly useful when things are moving too fast for the naked eye and brain to understand what is happening, which is often the case in sport.
Time is always plotted along the bottom (x-axis) and distance is always up the side (y-axis). The graph below shows a body that is stationary (not moving at all). As time passes the distance does not change… simple! Think of a sporting example other than a racing car sat on the start line.
The graph below shows a body moving at constant velocity. As time passes the distance increased uniformly. Note the gradient of this graph is equal to the speed of the body (speed – distance/time). So in this example speed = 2m / 10s = 0.2 m/s. Think of an example in sport other than the racing car cruising at a constant speed on the home straight having passed the chequered flag?
The graph below shows a body accelerating. The change in distance increases and time passes so it must be getting faster and faster.
The graph below shows a body decelerating. The change in distance decreases as time passes so it must be slowing down.
A velocity against time graph shows how fast a body was going at a particular instant in time. Time is always plotted on the bottom (X-axis) and velocity is up the side (Y-axis). This could be useful for coaching analysing a 100m sprint where the velocity of the athlete will change throughout the race.
The graph below shows velocity is not changing as time passes (so the body is moving at a constant velocity)
The graph below shows a body accelerating, for example, a sprinter during the first 20m of a 100m race.
The graph below shows a body decelerating, for example, the same sprinter during the last 20m of a 100m sprint.