1 / 21

US Customary Measurement System

US Customary Measurement System. The U S Customary Measurement System. System of measurement used in the United States Similar to the British Imperial System of Measurement, but not identical. Common Items: Size Comparison. Recording Measurements. A measurement always includes units

vinny
Télécharger la présentation

US Customary Measurement System

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. US Customary Measurement System

  2. The U S Customary Measurement System • System of measurement used in the United States • Similar to the British Imperial System of Measurement, but not identical

  3. Common Items: Size Comparison

  4. Recording Measurements • A measurement always includes units • A measurement always includes error • A measurement is the best estimate of a quantity • Scientists and engineers often use significant digits to indicate the uncertainty of a measurement • Indicate the accuracy and precision of your measurement

  5. Precision and Accuracy • Precision (repeatability) = The degree to which repeated measurements show the same result • Accuracy = The degree of closeness of measurements of a quantity to the actual (or accepted) value High Accuracy Low Precision Low Accuracy High Precision High Accuracy High Precision

  6. Recording Measurements • Ideally, a measurement device is both accurate and precise • Accuracy is dependent on calibration to a standard • Precision is dependent on the characteristics and/or capabilities of the measuring device and its use • Record only to the precision to which you and your measuring device can measure

  7. Significant Digits • Accepted practice in science is to indicate uncertainty of measurement • Significant digits are digits in a decimal number that carry meaning contributing to the uncertainty of the quantity • The digits you record for a measurement are considered significant • Include all certain digits in a measurement and one uncertain digit • Note: Fractions are “fuzzy” numbers in which significant digits are not directly indicated

  8. Recording Measurements • General Rules • Digital Instruments: Read and record all the numbers, including zeros after the decimal point, exactly as displayed • Decimal Scaled Instruments: Record all digits that you can certainly determine from the scale markings and estimate one more digit • Preferred over fractional scaled instruments • Fractional Scaled Instruments: Need special consideration

  9. Fractional Length Measurement • A typical ruler provides • A 12 inch graduated scale in US Customary units • Each inch is graduated into smaller divisions, typically 1/16” increments

  10. The Inch • The divisions on the U S Customary units scale are easily identified by different sized markings. The largest markings on the scale identify the inch.

  11. The Inch • Each subsequently shorter tick mark indicates half of the distance between next longer tick marks. • For example the next smaller tick mark indicates half of an inch = ½ inch 1/2

  12. The Inch • Half of a half = ¼ inch. An English scale shows ¼ inch and ¾ inch marks. • All fractions must be reduced to lowest terms. 1/4 3/4

  13. The Inch • Half of a quarter = 1/8 inch 7/8 1/8 3/8 5/8

  14. The Inch • Half of an eighth = 1/16 inch 1/16 9/16 5/16 13/16 3/16 7/16 11/16 15/16

  15. Measurement: Using a Fractional Scale • How long is the rectangle? • Let’s look a little closer

  16. Measurement: Using a Fractional Scale • How long is the rectangle? • What fraction of an inch does this mark represent? 3/16 1/4 1/2 1/8

  17. Measurement: Using a Fractional Scale • How long is the rectangle? What is the midpoint of 2 1/8 and 2 3/16? 5/32 3/16 1/8

  18. Measurement: Using a Fractional Scale • How do we determine that 5/32 is midway between 1/8 and 3/16? • Convert each fraction to a common denominator: 32 5 Find the average of the two measurements

  19. Recording a Measurement: Using a Fractional Scale • How long is the rectangle? • Remember the General Rule • Fractional Scaled Instruments require special consideration • Are 6 significant digits appropriate??? • 1/16 in. = .0625 in.

  20. Recording a Measurement: Using a Fractional Scale • For the standard ruler marked in 1/16 inch increments (least count = 1/16 in.) • Record fraction measurements to the nearest 1/32 inch • Record decimal equivalent to the nearest hundredths of an inch • Record with your data • The least count of the scale (1/16 in.) • The increment to which measurements are estimated (nearest 1/32 in.) 5 32 2 in. 2.16 in.

  21. Your Turn Record each measurement in fractional and decimal inches.

More Related