 #### Distance and Length

Distance and length are two very important measurements in the metric system. There are many different ways to measure distance and length. One of the most common ways to measure these quantities is to use a meter stick. You will learn to use a meter stick to obtain accurate measurements.

You will use distance and length measurements regardless of how far you go in science. Whether you wish to know the distance to a particular star or the size of tiny organelles inside a cell, size measurements are basic to all fields of science.

Distance is the amount of space between two different points or objects. One example is the distance from where you are sitting to the door.

• Think of five other examples of distances.

Length is the measurement of an object from one end to another. One example is the length of a table.

• Can you think of five other examples of lengths? Are there any differences between distance and length?

#### The Meter Stick

The basic unit of length in the metric system is the meter. A meter stick is exactly one meter long and is a very useful instrument in science.

You can use a meter stick to measure objects and lengths less than a meter and more than a meter. Let’s begin by learning how to measure lengths of less than a meter. To do this, you need to take a careful look at the meter stick.

A quick examination of a meter stick tells you much about the logic of the metric system as a whole. Below, you see the largest numerals you will see on a meter stick (i.e. 10, 20, 30, and so on). These represent the number of centimeters from the left end (zero end) of the meter stick as you look at it. You can easily see that there are 100 cm in a meter (notice that the last major mark is 90 rather than 100, which would be at the extreme right end of the stick if it were labeled). At the exact center of the meter stick is the 50 cm mark. If you placed your finger under the meter stick and held it up at this point, you would find it to be nearly balanced. That is because 50 cm is exactly one half of a meter. At this point you now know that a meter consists of 100 centimeters equally spaced along its length. To see centimeters better, examine the section of a meter stick enlarged between the left (zero) end of the stick and the 10 cm mark: In this enlarged view, you see the second largest numbers on the meter stick, representing individual centimeter markings. This enlarged section of the meter stick only contains just over 10 cm.

In this view, the finest units represented on standard meter sticks (millimeters, mm, or 1/1000 m) are also visible. If you were to count every one of the small millimeter marks on your meter stick you would find that there are 1000 of them.

Therefore, every meter is equally divided into 100 centimeters and 1000 millimeters. Centimeters are abbreviated as cm. Millimeters are abbreviated as mm. You use cm and mm regardless if we are talking about one or many of the units. That is, you would record 13 cm or 117 mm rather than 13 cms or 117 mms.

Whenever you record metric measurements, you must include the correct units. Recording a number without a unit is meaningless. For example, if you were to record a length of 48, what would this mean? It could be 48 millimeters (about the width of three fingers) or 48 meters (nearly half the length of a soccer field)!

#### LabLearner Tabs: The Meter Stick and Metric Ruler

Learn more about the meter stick by clicking on one of the tabs below. Start with Tab One: Using the Meter Stick. Then move on to the next tab, Tab Two: Example Meter Stick Measurements for examples of meter stick readings. The metric ruler is used identically to the meter stick. ## Using the Meter Stick

1. When measuring an object, you can align the 0 cm mark at the end of the meter stick with one edge of the object being measured. 2. Place the meter stick across the object being measured and read the meter stick at the other end. In the picture below, we see that the length of the book is about 22.8 cm. 3. Sometimes it is difficult to read from the zero end of a meter stick or ruler. The is particularly true if the end of the stick has been damage by repeated dropping, in which case it may become rounded without a straight edge for accurately aligning the end.

Therefore, another, and often more accurate way to take a length is to aline one edge of your sample with a position on the meter stick that is NOT at the end. In the example below, the edge of the book is aligned with the 10 cm mark on the meter stick. 4. When you use an internal marking on the meter stick, you must be sure to subtract the amount you started from the end of the stick from your final reading.

In the picture below, the reading is close to 33.8 cm. However, you must now subtract the 10 cm from the end you began with. This give you 33.8 cm – 10 cm = 22.8 cm. Recall that this was the same reading you got when you read from the end of the meter stick above. Lengths under a meter are often reported in centimeters (cm). Let’s look at five examples of meter stick readings that are less than a meter.

Example One: 8 cm Example Two: 16 cm Example Three: 16.3 cm  Example Four: 76.5 cm  Example Five: 99.6 cm  