Читать книгу Physics I For Dummies - Steven Holzner - Страница 35

In a measurement, significant digits (or significant figures) are those that were actually measured. Say you measure a distance with your ruler, which has millimeter markings. You can get a measurement of 10.42 centimeters, which has four significant digits (you estimate the distance between markings to get the last digit). But if you have a very precise micrometer gauge, then you can measure the distance to within one-hundredth of that, so you may measure the same thing to be 10.4213 centimeters, which has six significant digits.

By convention, zeroes that simply fill out values down to (or up to) the decimal point aren’t considered significant. When you see a number given as 3,600, you know that the 3 and 6 are included because they’re significant. However, knowing which, if any, of the zeros are significant can be tricky.

The best way to write a number so that you leave no doubt about how many significant digits there are is to use scientific notation. For example, if you read a measurement of 1,000 meters, you don’t know if there are one, two, three, or four significant figures. But if it were written as meters, you would know that there are two significant figures. If the measurement were written as meters, then you would know that there are four significant figures.