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The International System of Units (SI )

SI Measurement System. The International System of Units (SI ). The International System of Units (SI) is a system of units of measurement consisting of seven base units Mostly widely used system of measurement

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The International System of Units (SI )

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  1. SI Measurement System The International System of Units (SI) • The International System of Units (SI) is a system of units of measurement consisting of seven base units • Mostly widely used system of measurement • The United States is the only industrialized nation that has not adopted the SI system

  2. The International System of Units • Often referred to as the metric scale • Prefixes indicate an integer power of 10

  3. Common Items: Size Comparison

  4. Recording Measurements • A measurement always includes a value • A measurement always includes units • A measurement always involves uncertainty • A measurement is the best estimate of a quantity

  5. Significant Digits Scientists and engineers often use significant digits to indicate the uncertainty of a measurement • Significant digits are digits in a decimal number that carry meaning indicating the certainty of the value • All digits you record for a measurement are considered significant • Include all certain digits in a measurement and one uncertain or estimated digit

  6. Significant Digits • General Rules • Digital Instruments – Read and record all digits, 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

  7. Metric Scale • A typical metric scale often includes a30+ centimeter graduated scale • Each centimeter is graduated into 10 millimeters

  8. The Millimeter • The millimeter is the smallest increment found on a typical metric scale 1 mm

  9. The Millimeter • The next larger marking on a metric scale shows 5 millimeters 5 mm

  10. The Millimeter • Largest markings on a metric scale represent centimeters (cm) • These are the only marks that are actually numbered 1 cm = 10 mm

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

  12. Measurement: Using a Decimal Scale • How long is the rectangle?

  13. Recording a Measurement • How long is the rectangle? • Remember the general rule • Decimal Scaled Instruments – Record all digits that you can certainly determine from the scale markings and estimate one more digit Best Estimate = 3.84 cm

  14. Recording a Measurement • How long is the rectangle? • Remember the general rule • Decimal Scaled Instruments – Record all digits that you can certainly determine from the scale markings and estimate one more digit Best Estimate = 3.84 cm Certain

  15. Your Turn • How would you record the length of this rectangle? • How many significant digits? 6.33 cm 3

  16. Your Turn Record each measurement in centimeters using the appropriate number of significant digits.

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