Overview
This lecture explains how to accurately measure length using a ruler, emphasizing reading graduations, estimating values between marks, and identifying measured versus estimated digits.
Understanding the Ruler
- Examine the ruler to identify the unit and the meaning of each tick mark or graduation.
- Each numbered tick mark on the ruler represents 1 centimeter (cm).
- Smaller, unnumbered tick marks represent 0.1 centimeters (1 millimeter).
Measuring Process
- Place the object so its edge aligns with the ruler’s scale.
- Find where the object ends: identify which centimeter mark it is past, but not beyond the next one.
- The first digits of your measurement (before the decimal) come directly from the ruler.
Estimating Between Graduations
- If the object's end falls between two tick marks, estimate its position for increased accuracy.
- The digit you estimate beyond the smallest graduation is called the "estimated digit."
- For example, if the line is just past 2.5 cm but before 2.6 cm, you might record 2.55 cm.
Measured vs. Estimated Digits
- Digits you read directly from the ruler are "measured digits."
- The digit you estimate is the "estimated digit," indicating uncertainty and measurement precision.
Key Terms & Definitions
- Graduation — a line or mark indicating a specific measurement on an instrument.
- Measured Digit — a number read directly from the measuring device.
- Estimated Digit — the number you judge or estimate between the smallest graduations.
- Centimeter (cm) — a metric unit of length; 1 cm = 10 millimeters.
Action Items / Next Steps
- Practice measuring objects using a ruler and identify both measured and estimated digits in your answers.