Speed

Speed is derived from distance and time. This is written as:

v = d/t

d is (usually) measured in metres, but can also be measured in other units such as km, cm and mm
t is (usually) measured in seconds, but can also be measured in other units such as minutes and hours
Therefore, v is usually stated in metres per second (m s^-1). However, when other units are used for distance and time, we can have other units such as km hr^-1.

NOTE #1

1 km hr^-1 = 0.277 m s^-1
1 m s^-1 = 3.6 km hr^-1

NOTE #2

This equation only works for uniform motion (constant speed or stopped).

From Graphs

Speed can be calculated from a d-t graph by finding the gradient (rise/run).