Interpreting a Displacement Vs Time Graph (basic) 
Let's take a look at a basic (straight line) displacement vs time graph: Notice that the TYPE of graph tells us helpful/interesting information:
The SHAPE of the graph tells us even more helpful information
Whether the graph is a line or a curve is also significant. A curve tells us that the object's velocity is itself changing (since the slope of a curve is changing). A straight line tells us that the object's velocity is constant
THEREFORE: We can analyze the graph above and get a lot of information BEFORE we even work with the actual numbers: An initial analysis of the graph above shows that:
Between 5 seconds and 8 seconds:
Between 8 seconds and 13 seconds:
NOTICE that there is NO transition time for the object to slow down, speed up or stop. That is truly impossible in the REAL world (except perhaps in quantum mechanics, but I digress), but in physics, we frequently use such basic situations to help us understand basic physics concepts.
