To prevent the communication problems, scientist developed a standard of measurements which is internationally accepted. Insert cartoon of two people talking. One just completed a run, and tell the other that he completed 100 mete rs in 9 seconds. The other commends him on such a fast time. There is an international system of units from which all other measurable physical quantities are derived from. This system of fundamental quantities is called the SI system, from the French words Systeme International d'unites.

The ones that will be used most in this section are length, mass and time.