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Measuring Force!

  1. Oct 10, 2008 #1
    Can you measure a force?
     
  2. jcsd
  3. Oct 10, 2008 #2

    Andy Resnick

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    Not directly. There is no such thing as a force-o-meter.

    Devices like strain gauges, acclerometers, scales, etc. can be used to measure a force only if they have a known stress-strain relationship.

    AFAIK, the only things we can directly measure are length, time, and (maybe) charge. Every other measuring device- thermometers, strain gauges, voltmeters, etc convert the direct measurement into what we 'measure' (pressure, force, voltage...) by a calibration step, that is comparison with a standard.
     
  4. Oct 10, 2008 #3
    yes... what do you think a weighing machine reads?
     
  5. Oct 10, 2008 #4

    FredGarvin

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    What? Are you asking or telling? We can not directly measure a force as Andy pointed out. A "weighing machine" as you put it, measures the deflection in a spring. That deflection is calibrated to give a force based on the particular spring constant. Most of the standard types of gauges rely on the measurement of deflection at the core to give you a desired quantity. Even that aside, you never really measure a force, you measure a pressure which is then assumed as the force over a specific area.
     
  6. Oct 10, 2008 #5
    what force do you think causes the pressure-or-whatever u say?

    Pressure...?
     
  7. Oct 10, 2008 #6

    stewartcs

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    Don't forget about mass!

    CS
     
  8. Oct 10, 2008 #7

    russ_watters

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    Staff: Mentor

    Question asked and answered. Thread locked.
     
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