100903 - Physics 121 9/3/10 Theme Music: Paul Simon When...

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Physics 121 9/3/10 Prof. E. F. Redish 1 Theme Music: Paul Simon When numbers get serious Cartoon: Bill Waterson Calvin & Hobbes 9/3/10 Math is different in science from in math class! • Math in physics is fundamentally about relationships among measurements , not primarily about calculating – or even solving (though we do some of that). • Functional dependence is critical. “More of this means more of that” is not good enough. How much more matters. 9/3/10 7 An example from a math exam • Writing the equation in this problem on a physics exam would receive 0 credit and the comment: “This is a meaningless equation!” The population density of trout in a stream is where r is measured in trout per mile and x is measured in miles. x runs from 0 to 10. (a) Write an expression for the total number of trout in the stream. Do not compute it. 9/3/10 8 r ( x ) = 20 1 + x x 2 + 1 How would you fix this?
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Physics 121 9/3/10 Prof. E. F. Redish 2 Third icon: Measurement • As we learned with our example, often our perceptions play us false. • In order to be sure we understand what is going on we need to quantify. In order to do that we need to invent a process to assign a number to a physical quantity – measure. 9 9/3/10 Measurement is basically about counting. 9/3/10 10 N Perim Area Vol 1 2 3 11 Operational definitions • In science we often define something by telling how it is measured,
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This note was uploaded on 12/28/2011 for the course PHYSICS 121 taught by Professor Shawhan during the Spring '10 term at Maryland.

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100903 - Physics 121 9/3/10 Theme Music: Paul Simon When...

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