si units of measurements
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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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.
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Base Units and Derived Units
• SI has 7 metric units known as base units, • which are as follows.
Quantity Unit Symbol
Length meter m
Mass kilogram kg
Temperature Kelvin K
Time second s
Amount of substance
mole mol
Electric current
ampere A
Luminous Intensity
candela cd
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Derived Units Additional SI Units, which are made from a combination of base units
ex. Area, Volume, Density etc.
Quantity Unit Symbol
Area Square meter m²
Volume Cubic meter m³
Density Kg per cubic meter Kg/m³
Frequency hertz Hz
wavelength meter m
VelocitySpeed
m/s directionm/s
v v7
Acceleration Meters per second per second
m/s² or m/s/s
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Quantity Unit Symbol
Power J /s W
Force Kg.m/s² N
Momentum Kilogram meter per s Kg.m/s
Work Joule J
Energy Joule J
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•
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 length
c
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).
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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
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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: Temperature Celsius Fahrenheit Kelvin
Symbol °C °F K
Melting point of ice 0 32 273
Boiling point of water
100 212 373
-273 -460 0
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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
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Conversions: Units based on 10
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Conversions
C/100 = (F-32)/180
Celsius = 5/9 X (Fahrenheit -32)
Fahrenheit =( 9/5 x Celsius) + 32
Kelvin = Celsius + 273
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• 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 year is equal to the distance that light travels through space in one year (9.46 × 1012 km)
Units of distance in space
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Accuracy & Precision in Measurement
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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.
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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.