THE MEASURE OF THE FUNDAMENTAL MAGNITUDES

To measure is comparing a magnitude (M) with the corresponding unit (u) to determine how many times M contains u.

1- Weight is measured by balancing two forces of opposite senses.

2- Length is measured by sliding a graduated tape over the object.

3- Temperature is measured by the expansion or contraction of a liquid (mercury or alcohol) enclosed in a graduated glass tube.

4- Time is measured by counting equal intervals of an uniform periodic movement and therefore predictable. In a clock of hands the minute hand executes, in an hour, a complete return. One hour, for example, is not a measure of movement, but of its duration. The measures of movement are distance and speed. Clocks count time intervals.

Elvis Sibilia