From: heathjohn2@gmail.com   
      
   On Monday, August 6, 2018 at 3:26:40 AM UTC-4, Tom Roberts wrote:   
   > On 8/5/18 12:24 AM, Sylvia Else wrote:   
   >> On 5/08/2018 10:28 AM, Luigi Fortunati wrote:   
   >>> I entered the elevator, I placed an electronic scale on the floor and,   
   >>> after starting, when the elevator bought steady speed uphill, I weighed   
   >>> myself and the display showed 83.5 kg.   
   >>>   
   >>> I repeated the operation during the descent at constant speed and the   
   >>> display showed a weight of 83.2 kg.   
   >>>   
   >>> Is it a strange result or does it correspond to the theory?   
   >>   
   >> I corresponds with the fact that electronic scales results are not   
   >> particularly reproducible, with a variation between measurements that is   
   >> less than 1% being not at all surprising. Vibration, muscle twitches,   
   >> etc. all contribute.   
   >   
   > Yes. Typical bathroom scales are rather limited in accuracy. I suspect   
   > his scale will vary by at least that 0.3 kg, weighing the same object   
   > multiple times.   
   >   
   > Using my electronic scale, when I weigh myself five times in a row the   
   > results vary by typically 0.4 or 0.6 pounds (the resolution of the   
   > display is 0.2 pounds). Moreover, I must weigh something else between   
   > measurements, because it clearly remembers the previous value and   
   > settles to it very quickly. So between weighings I sit down and measure   
   > just my legs. If I attempt to weigh myself standing on tip-toe, it   
   > usually times out with an error, because I cannot hold myself steady enough.   
   >   
   > 	(Experimental physicists apply their knowledge and   
   > 	 experience to everything.)   
   >   
   > Tom Roberts   
      
   This is an interesting question. Yes a little friction in the scales   
   could lead to a hysteresis in the measurement for 83.2 vs 82.5   
   Kg. However this is a thought experiment for the theoretical results so   
   perfect scales may be assumed as well as zero change in gravity   
   gradient.   
      
   Under ideal condition of constant speed up and down how much does one   
   weigh. Let us call the weight 100 pounds for an even number and the   
   down and up speed 9 meters per second. If the elevator were to   
   accelerate at 9 meters per second squared then the weight should be 0   
   pounds moving down and 200 pound moving up. However the elevator is not   
   accelerating rather moving at a constant speed of 9 meters per   
   second. This makes for a complicated mix of a nonlinear gravity falling   
   rate of 9 meters per second squared with linear constant speed of 9   
   meters per second. With this in mind the down trip weight over time   
   should be 0 10 99 99.9 99.99 ... pounds. The up trip should be 200 190   
   101 100.1 100.01 ... pounds. Its weight would depend on when it is   
   measured. Note there is an energy conservation concern the numbers   
   given. The energy up must equal the energy down and 101 up does not   
   equal 99 down ,, what went wrong ?   
      
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