AI Tutor
If you try to measure a 2-meter physics track using a standard 30 cm classroom ruler, you have to lift, slide, and line up the ruler seven separate times. Every single time you move that ruler, tiny alignment errors add up.
A meter stick solves this by giving you exactly one meter (1 m1\text{ m}) of continuous measurement in a single rigid tool.
Before you take a single reading in the lab, how do you quickly switch between meters, centimeters, and millimeters without losing track of your decimal point?

The Metric Ladder: m, cm, and mm

The metric system uses prefixes based on factors of 10. The prefix centi- means one-hundredth (10−210^{-2} or 1100\frac{1}{100}), while milli- means one-thousandth (10−310^{-3} or 11000\frac{1}{1000}).
Because every step is a power of 10, converting between units simply means shifting the decimal point left or right.
Knowing the numbers is one thing, but how do you physically line up a meter stick to ensure your measurement is accurate?

Proper Technique and Parallax Error

Always position your eye directly perpendicular to the mark you are reading. Looking at an angle causes parallax error, which is the apparent shift in an object's position when viewed from different angles.
What happens when the object you are measuring is longer than the meter stick itself?