Physics Help Forum Should the word "relative" be used when discussing kinetic energy of Systems?
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 Oct 5th 2016, 03:14 AM #1 Junior Member   Join Date: Oct 2016 Posts: 3 Should the word "relative" be used when discussing kinetic energy of Systems? If you placed a jar of ideal gas that is well insulated, in a car and had a temperature transmitter monitoring the gas temperature in the jar and then drove the car around - would there be a change in temperature- afterall the average kinetic energy of the molecules has increased? - however the kinetic energy of the molecules has not increased relative to the transmitter - so there would be no increase in temperature as you might intuitively expect. So should the term "relative" be used when discussing kinetic energy
 Oct 5th 2016, 05:32 AM #2 Physics Team     Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,322 KE is calculated from $\displaystyle KE=\frac 1 2 m v^2$ , and velocity is measured relative to the observer. So yes - the calculation of KE is relative to the observer. For that matter we know from Einstein's Theory of Relativity 'm' is also relative. Hence an object's KE is not absolute. topsquark likes this. Last edited by ChipB; Oct 5th 2016 at 05:37 AM.

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