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					Objects and Properties
• Objects : physical "things" in our environment
• Properties of objects
   – those qualities that make an object what it is
• Referent (reference)
   – how we view things due to our experiences
   – our window to the world
   – in physical science we need common referents
     (references) by which to study our physical universe
• in science we need to eliminate vagueness in
  communication
• we do this by having standard measurements with
  which to make comparisons between objects
• A measurement consists of two parts:
  – numerical value: describes how big the measurement is
  – unit: tells us what the measurement is in; e.g., meters,
    kilograms, cubic centimeters, etc.
     • the unit also shows the type of measurement we are making;
       e.g., length, mass, volume, etc.
           Making a measurement

• A measurement consists of three activities:
  – choose a referent (reference), which will be your unit of
    measurement
  – compare the property you want to measure to the chosen
    reference (unit)
  – count the units (in the chosen reference)
• Standard Units
  – in science a set of standard measuring units are used to
    ensure that measurements can be duplicated by others
• Two major systems of standard units:
  – Metric System
     • Used throughout the world
     • Based on powers of 10
  – English System
     • units which corresponded originally to parts of the human body
• Many early units for measurement were originally based on the
  human body. Some of the units were later standardized by
  governments to become the basis of the English system of
  measurement.
• Area (the size of a surface) can be described by two length
  measurements. Volume (the space an object occupies) can be
  described by three length measurements. Length, however, can be
  described only in terms of how it is measured, so it is called a
  fundamental property. Area and volume are called derived
  properties.
    Fundamental (Base) and Derived
             Properties
• Fundamental (base) property
  – defined by itself, independent of other properties
  – Fundamental (base) properties are:
    • length, mass, time, temperature, electric current
• Derived property
  – defined in terms of fundamental properties
    (depends on fundamental properties)
  – Examples: surface area, volume, speed (speed is
    distance divided by time), etc.
• Metric system (MKS) - also called International
  System of Units (SI)

  Fundamental Properties     Base Unit     Symbol

  –   Length                    meter       m
  –   Mass                      kilogram    kg
  –   Time                      second      s
  –   Temperature               Kelvin      K
  –   Electric current          ampere      A
        Base Units for the Metric System
• Meter (m)
  – base unit of length: meter (m)
     1m = 3.28 ft (foot is the base unit of length in the English
    system)
• Kilogram (kg)
  – base unit of mass: kilogram (kg)
     • Mass represents the amount of matter (substance) contained in an object.
       The mass of an object is a measure of the inertia (resistance to movement) of
       that object.
     • Weight is the effect of gravity on an object.
     • The weight of an object changes with location, the mass of an object does
       not.
• Second (s)
  – base unit of time: second (s)
  (also the base unit of time in the English system)
       Each of the base units in the metric system can be
     modified with different prefixes which multiply out the
                    base unit by some factor
  Prefix         Symbol                     Meaning
• Giga             G                   1,000,000,000 times the
                                               base unit
• Mega              M                  1,000,000 times the base
                                               unit
•   Kilo            k                  1,000 times the base unit
•   Hecto           h                  100 times the base unit
•   Deka            da                 10 times the base unit
•   Deci            d                  0.1 of the base unit
•   Centi           c                  0.01 of the base unit
•   Milli           m                  0.001 of the base unit
•   Micro                             0.000001 of the base unit
•   Nano            n                  0.000000001 of the base
                                               unit
                      The Scientific Method
• Method for developing scientific knowledge
• Steps:
   – Hypothesis: possible explanation of a phenomenon
   – Experiments: test the hypothesis
      • If the hypothesis fails, revise it and retest
      • If the hypothesis passes, more experiments for more testing and greater
        confidence
   – An accepted hypothesis may result in a scientific principle or in a scientific law
• Scientific principle
       • An explanation concerned with a specific range of phenomena
• Scientific law
       • Describes a more general and important phenomenon than a principle
       • Expressed:
           – in verbal form
           – by an equation
           – by a graph
      Scientific Models and Theories
• Model
  – simulation of a real object or phenomenon
  – used to study something that cannot be observed directly
     • physical model - can be seen and touched
     • mental model - exists in the mind and helps us understand
       concepts
     • equation model - describes the variables involved and their
       relationship
• Theory
  – a broad, detailed explanation of a phenomenon
  – Hypothesis: statement before tests
  – Theory: has passed the test
     Scientific Statements and Data
• Must be testable (measurable)
• Data (or measurements) must meet two criteria:
  – Reliability
     • everyone agrees to the meaning of the data (measurements)
     • others can replicate the measurements (or the experiments) with
       the same results
  – Precision
     • Repeatable and reproducible measurements that conform to
       standards

				
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posted:10/12/2012
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