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SI Units Of Measurements

SI Units Of Measurements. Measurement make sense only, if it has both number and Unit. ex. 6 inches, 12 dollars. Some examples of units are inches, feet, pounds, degree F ahrenheit. A set of measuring units called SI, or the Inter national System of Units.

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SI Units Of Measurements

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  1. SI Units Of Measurements Measurement make sense only, if it has both number and Unit. ex. 6 inches, 12 dollars. Some examples of units are inches, feet, pounds, degree Fahrenheit. A set of measuring units called SI, or the Inter national System of Units. SI is a revised version of metric system, which was originally developed in France in 1791. The abbreviation stands for French name System International d’Unites.

  2. Base Units and Derived Units • SI has 7 metric units known as base units, • which are as follows.

  3. Derived UnitsAdditional SI Units, which are made from a combination of base units ex. Area, Volume, Density etc.

  4. 1) Length a . The distance from one point to another point. b. Base unit is the meter (m). c. Centimeter or inch ruler is used to measure lengthc 2). Mass • a. The amount of matter in a substance. • b. Base unit - kilogram (kg). • The tool used is a triple beam balance. (Grams g) 3). Temperature • a. The amount of kinetic energy a substance has. • b. SI unit is the Kelvin (K).

  5. Volume a. The amount of space a substance occupies. For regular shaped solids use the equations L X W X H. but for an irregular shaped solid we use a graduated cylinder and measure how much water is displaced. ( m³ or L ) b. Base unit is the liter (L). 1 L = 1 m³

  6. Temperature • Definition – A measure of the heat of an object • Thermometer – A device that measures temperature, • usually with mercury. • There are three temperature scales . • 1) Fahrenheit scale. 2) Celsius scale 3) SI Unit scale or Kelvin scale. • Some baseline temperatures in the three different temperature scales:

  7. International system of units (SI) • Used in many countries to have a uniform scale of measurement. • 1. Based on multiples of 10 Common metric prefixes

  8. Conversions: Units based on 10

  9. Conversions C/100 = (F-32)/180 Celsius = 5/9 X (Fahrenheit -32) Fahrenheit =( 9/5 x Celsius) + 32 Kelvin = Celsius + 273

  10. Units of distance in space • An “Astronomical Unit” (AU) is a convenient way to measure distances in the solar system. • It is the average distance from the earth to the sun, about 150 million kilometers (1.5 X 108 km or 93 million miles) • 1 mile = 1.6 km. • One light yearis equal to the distance that light travels through space in one year (9.46 × 1012 km)

  11. Accuracy & Precision in Measurement

  12. Precision Depends on the How finely tuned your measurements are or how close they can be to each other. It depends on measuring tool. Determined by more number of significant digits. If the analog clock is showing 5 minutes and the digital clock is showing 5 minutes 15 seconds, the digital clock is showing more precise measurements.

  13. Accuracy: • How close you are to the actual value • Depends on the person measuring • Even if the digital clock is more precise by showing 5 minutes 15 seconds but if it is running slow. Although the clock is precise to the nearest seconds, the time displayed is not accurate.

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