How to convert Joules(kinetic energy) plot chart into watts? Anyone know how?enter image description here

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    $\begingroup$ Watts are Joules per second, so area under the curve. $\endgroup$
    – Solar Mike
    Oct 4, 2018 at 3:24
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    $\begingroup$ @SolarMike But the area under the curve would give Joules times seconds, which seems a meaningless quantity. Using the slope of the curve would be better! $\endgroup$
    – alephzero
    Oct 4, 2018 at 8:28
  • $\begingroup$ Why you don't plot it in Watts? Solidworks does plot in Watts. $\endgroup$
    – user14407
    Oct 4, 2018 at 10:31
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    $\begingroup$ @SolarMike I think you're thinking of the other way around. To get total energy from a power plot you just integrate. $\endgroup$
    – JMac
    Oct 4, 2018 at 14:36
  • $\begingroup$ Yeah; the differential is tan( angle of the curve ) or rise rate. $\endgroup$
    – SF.
    Oct 5, 2018 at 12:33

1 Answer 1


To convert a plot of J versus s to a plot of J/s vs s, take the derivative.

Here is my quick-and-dirty answer after digitizing the data.

derivative plot

  • $\begingroup$ What software package[s] did you use here? $\endgroup$ Oct 4, 2018 at 22:23
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    $\begingroup$ IgorThief in Igor Pro. WaveMetrics.com. When I would have the raw data rather than image, this would be a direct one-step process that would be accurate rather than rough. $\endgroup$ Oct 4, 2018 at 22:51
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    $\begingroup$ @Chemomechanics my favorite tool for digitizing graphs is DataThief. It's like magic. $\endgroup$ Oct 5, 2018 at 16:53

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