# Chpt_3 - 3 Fundamental Quantities, Forces, and Energy...

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3 Fundamental Quantities, Forces, and Energy Perception Cycle V4 Env Att Stim.png Fundamental Concepts in this Lecture 1. Operational Definitions tell us how we measure something 2. Basic quantities: length, time, mass, charge 3. Basic quantities are combined to produce derived quantities 4. In measuring motion, we have displacement, velocity, and acceleration as derived quantities 5. In measuring space, we have length, area, and volume as derived quantities 6. Density is a derived quantity formed by dividing the amount of mass by the amount of volume of an object Fundamental quantities and how to define them Understanding light, sound, and their associated perceptions, requires that you recognize they have powerful physical principles and concepts at their roots. We begin here with some quantities or properties that we can measure, and laws and principles that relate them. We rarely view terms like position, mass, and force as being full of romance and mystery. Yet, they are the foundations for opening the door on the truly fascinating and mysterious world around us. Even alone, they harbor deep mysteries. We describe light and sound in

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terms of properties like position, pressure, or forces that repeat, or oscillate over time. Concepts like mass, position, and wavelength are so fundamental that simple questions about them can bump us up against the limits of what is known. Science does not ignore these questions. But to keep from stalling on these imponderables, we often fall back to what we can observe, or measure. Definitions that do this differ in important ways from Dictionary Definitions. Definitions of this class focus on how we measure something rather than what it is or means. Oh, the meaning of the idea is not ignored in these definitions, it is just not the main focus. Let us construct one of these definitions. A College Sophomore is a term that behaves this way nicely. For the purposes of this example, we define a college sophomore as someone who meets the following conditions. 1) They are a matriculated student (meaning that they have enrolled in the university for the purpose of getting a degree), and 2) they have completed more than 32 semester hours, but less than 64 semester hours of credit. Notice that we have listed the steps or operations necessary to observe or measure whether someone is a sophomore. For this reason, these are called Operational Definitions. In this case the steps are 1) Observe if they are enrolled to get a degree, 2) Count how many credits they have completed, and 3) See if the number of credits is within the boundaries of 32 and 64 credits. Occasionally we include math operations, such as divide, in our definitions. Operational definitions state or imply the steps needed to observe or measure a property.
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## Chpt_3 - 3 Fundamental Quantities, Forces, and Energy...

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