Basic Units

There are, in general, three basic things that we can measure for an object:

distance -- this covers length, width, height, radius, etc.

time -- duration

mass -- a measure of the amount of material in an object

When we measure these quantities, we must attach units to give the numbers meaning. Some units that Americans are most familiar with include

distance -- inches, feet, yards, miles

time -- seconds, minutes, hours, days, years

mass -- pounds, ounces, tons (although these are not truly measures of mass, so we have to be careful)

These units form what is known as the "English system" of units, a somewhat ironic name since the only country that uses them anymore is the United States! For scientific measurements, they have been superseded by the metric system.

We can switch back and forth between units, as long as we stick to the same category. For example, we can change a figure from feet to inches, or from yards to miles. This switching of units is called converting units. We cannot, however, change from feet into hours!

Let's start with a very simple example of conversion. We know that there are twelve inches in a foot. How many inches are there in two feet? If someone is six feet tall, how many inches is that? Go to the next page to check your answers.

Questions? Ask the designer, Jim Heath