Overview
This lecture explains how to use a ruler to measure length accurately, focusing on reading graduations and estimating digits for precise measurements.
Understanding the Ruler
- Examine the ruler to understand the units and tick marks (graduations) before measuring.
- Each large tick mark on a standard metric ruler typically represents 1 centimeter (cm).
- The unit of measurement (centimeter) is usually labeled on the ruler.
Reading Measurements
- Identify the interval between tick marks; on many rulers, small graduations represent 0.1 cm.
- When a line to be measured falls between two major marks (e.g., between 2 and 3 cm), the value is 2 point something cm.
Estimating Digits
- If the measurement falls between two tick marks, estimate the value to one additional decimal place.
- For example, if a line is slightly past 2.5 cm but before 2.6 cm, you might estimate it as 2.55 cm.
- The last digit in your measurement is the estimated digit, which reflects your best judgment between graduations.
Reporting Measurements
- Combine the digits read directly from the ruler with your estimated digit for a final measurement (e.g., 2.55 cm).
- The estimated digit increases the precision of your measurement beyond what is directly marked.
Key Terms & Definitions
- Graduation — a tick mark on a ruler indicating a specific measurement interval.
- Estimated digit — the digit you estimate between two marks when a measurement falls between them.
- Unit of measurement — the standard used to express a quantity (e.g., centimeters).
Action Items / Next Steps
- Practice measuring various objects with a ruler, estimating the last digit for increased accuracy.