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Rates? What are they

  1. Jun 30, 2015 #1
    In physics and Math, it was always understood that rates where a rate of change, typically per time such as speed and acceleration and such. But now I am confused.

    Different dictionary define rates as any measure, quantity, or frequency, typically one measured against some other quantity or measure. They give examples like $/pound, flowers/person, miles/gallon, miles/ hour

    So back to an earlier post, would that make pressure a rate? I know it is not a rate as in speed or anything like that. But I am curious I have never thought of it before and would like to know how others define pressure?

    In the end, I don't want to get more confused, I just want to simply know what a rate is and if this definition is true, should I somehow be defining pressure as rate?
     
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  3. Jun 30, 2015 #2

    phinds

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    I think in science you can take "rate" to mean "rate of change". Those other examples you gave (flowers/person for example) might somehow be considered a rate when using English, but not in technical terms.
     
  4. Jun 30, 2015 #3

    A.T.

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    Does it matter?
     
  5. Jun 30, 2015 #4

    anorlunda

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    Suppose we expressed pressure as KG/m^2. Does that make it a rate by your definition of rate? Force per unit area instead of force per unit time.
     
  6. Jun 30, 2015 #5
    I don't know, I guess I am thinking more less what PHINDS said, where we think of rates in science and such more as rates of change, rates based on time or how long something changes. Maybe in general terms that other definition applies and there for technically the other examples including pressure would be a rate, but as a previous poster stated, maybe I shouldn't care.

    I guess as long as I know what pressure is or speed as a rate, then maybe I shouldnot worry
     
  7. Jun 30, 2015 #6

    phinds

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    Yes, getting hung up on issues that arise out multiple definitions in the English language instead of well defined technical terms is generally a waste of time.
     
  8. Jun 30, 2015 #7
    Thank you, that is what I realized. I could stress about rates and what they mean and if pressure is one of them. In the end, I know what pressure is and its expressed lbs/in^2 so who cares. That and I also realized there are several definitions of rates: 1 Speed or rate of change(sciences), 2. Cost per item, 3. ratio or proportion. Well for what I do in my life, I don't think pressure really applies and taking a general definition and trying to apply it to all is more confusing than it is worth.

    Thank you again for clarifying and answering my dumb question.
     
  9. Jun 30, 2015 #8
    I agree with that.
    I think pressure is a rate, Force/area right.
    But what do I know I'm not a scientist.
     
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