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Defining mass resisting movement exerting energy

  1. Mar 22, 2003 #1
    I have read that mass can be measured by the degree of movement resistance to surrounding activity, so that an object high in mass will take more energy exertion to move than an object with a relatively lower mass measurement. Does anyone else have a different working definition for the word mass? Does the definition I have for mass not have any validity? If e=mc2 than does this mean that energy is measured by an objects potential to move surrounding fields of substance as well as an objects ability to resist a change in direction of movement once set in motion?

    Does a car traveling at 60 mph have an easily measured higher degree of mass as a result of the fact that it takes much more energy exertion to alter the position of a car at this speed than a stationary one or is it so that only objects moving at great speeds have a noticeable degree of mass increase?
  2. jcsd
  3. Mar 22, 2003 #2


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    Welcome to the Forums, Onon!

    Your description of measuring mass as inertia is a fairly acurate one. However, the example of a car in motion is not exactly what physicists mean by this. The amount of force the brakes must exert to bring the vehicle to a stop from this speed is almost the same as the amount of force the drivetrain was required to apply in order to accelerate to that speed. And by "almost the same", I should point out that the difference between the two is mainly due to friction of the moving parts and wind resistance. The amount that the cars mass increases at 60 mph is very small, almost impossible to measure.
  4. Mar 22, 2003 #3
    My understanding of E=mc2 is....
    mass x c2=Energy

    But then, I don't quite understand your question; I'd like to put a prepostition here and there, but it'd be better if you explained it..[?]
  5. Mar 22, 2003 #4
    How are you defining engery and inertia? What are your working definitions for these words?
  6. Mar 23, 2003 #5
    Of course, what do you think F = ma is?
    Mass is a measure of its resistance to acceleration.

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