MEASUREMENT

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MEASUREMENT

• We obtain an understanding of our environment by
  observing the physical world through
  measurements.
• Measurement is a comparison of physical quantity
  with a standard unit.

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MEASUREMENT

• It is expressed with numbers and units.
• Physical characteristics can be expressed in
  terms of fundamental quantities.
• Our comprehension of the physical world is based
  on fundamental quantities.

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FUNDAMENTAL QUANTITIES

• Four quantities have been identified and
  specified as
• fundamental.
• These are
• Length
• Mass
• Time
• Electric charge
• They form the basis for other quantities
• necessary to describe and understand the
• physical sciences.

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Length

• We use length to measure location or size.
• Length is defined as the measurement of space in
  any direction.
• Note Space has three dimensions, each is
  measured by length.
• Consider a box
• Length (l)
• Width (w)
• Height (h)

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Time

• Time is the continuous forward flow of events.
• Events allow us to precise time, without events,
  we have no innate awareness of time.

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Mass

• Mass quantifies matter.
• Mass refers to the amount of matter an object
  contains.

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Electric Charge

• Electric Charge is the property associated with
  some particles, that gives rise to electric
  forces and electrical phenomena.

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STANDARD UNITS

• A standard unit is a fixed and reproducible value
  for the purpose of taking accurate measurements.
• A set of standard units is referred to as a
  system of units.

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British System

• British System uses the familiar unit of
• Length foot
• Mass Slug
• Weight pound
• Time Second
• Electric Charge Coulomb
• Note It is also called the Gravitational System
  of Units.

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Metric System

• Metric System is considered to be simpler
• than the British System as the conversion is by a
  
• factor of ten.
• The standard units of
• Length meter, m
• Mass kilogram, kg
• Time seconds, s
• Electric Charge Coulomb
• They are called the International System of Units
  (SI
• units).

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Systems of units

• Metric System
• Length meter, m
• Mass kilogram, kg
• Time seconds, s
• Electric Charge - Coulomb

• British System
• Length foot
• Mass Slug
• Time Second
• Electric Charge Coulomb
• Weight pound

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International System of Units

• There are seven base units of the International
• System of Units.
• Meter, m, measures length.
• Kilogram, kg, measures mass.
• Second, s, measures time.
• Ampere, A, measures electric current.
• Kelvin, K, measures temperature.
• Mole, mol, measures amount of substance.
• Candela, cd, measures luminous intensity.

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Derived Quantities

• Derived Quantities are formed by combining two or
  more of the fundamental quantities.
• Examples
• Area length x width
• Volume length x width x height
• Speed distance/time
• Density mass/volume

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Density

• Density refers to how compact or crowded a
• substance is, that is, the amount of mass
• located in a definite volume.
• Density is simply the mass per unit volume.
• Density mass/volume

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Measurement Errors

• Systematic Errors
• Systematic errors are associated with instruments
  or the technique used.
• They are as a result of
• Improperly calibrated instrument
• Error incurred from observers reading

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Measurement Errors

• Random Errors
• Random Errors result from unknown and
  unpredictable variations in experimental
  situations.
• Such as fluctuation in electrical voltage.
• Changes in temperature, pressure, etc

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Accuracy / Precision

• Accuracy indicates how close measurement comes to
  the true value.
• Precision refers to the agreement among repeated
  measurement, that is, how close they are
  together.

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Converting Quantities

• Use a conversion factor, a ratio relating
• one unit to another.
• Choose the appropriate form of the conversion
  factor(s) so that the unwanted units cancel.
• 3. Check to see that the unit cancel and that
• you obtain the desired unit.

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Converting Quantities

• Desired quantity and units given
• quantity and units x conversion factor

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Common relationships

• 1 kg 2.2 lbs.
• 1 lb. 453.6 g
• 1 inch 2.54 cm
• 1.06 qt 1 L
• 1.0 mile 1.609 km

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Temperature

• A measure of hotness or coldness of an
• object .
• Types of temperature scales
• Fahrenheit on this scale the normal freezing and
  boiling points of water are taken to be 32?F and
  212?F respectively.
• Celsius Boiling point is 100?C and the freezing
  point is 0?C

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0ºC 32ºF
32ºF
0ºC
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100ºC 212ºF
0ºC 32ºF
0ºC
100ºC
212ºF
32ºF
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Relationship Between oC and oF
oF 1.8 oC 32

• There is no direct relationship between K
• and oF. Therefore, one must go through oC
• in order to get temperature in K.

K oC 273