|MadSci Network: Physics|
Greetings: Your observations of spinning water and softdrink filled glasses are interesting. I could not find any data on the difference in volume and weight between carbonated and flat drinks so I tried several experiments to measure these parameters and to duplicate your results. First, I measured the volume change between flat and carbonated Sprite and Pepsi and water in case there might be a significant change in volume and or weight. I found that the volume of flat Sprite was only 3% less then the freshly opened carbonated drink and that Pepsi had only a 2% volume reduction when flat. The weight loss from the freshly opened carbonated Pepsi drink to the flat drink was only 0.7%. From this I conclude that there is not a significant change in weight and a very small volume difference between flat or carbonated soft drinks and flat water. I could not find a crystal glass with a slightly rounded bottom so I used one half of a thin polystyrene sphere of the type that are available in craft stores to make Christmas ornaments etc. I could then set many different types of glass containers, including heavy crystal glasses, in the half sphere and spin them like a top. I could find no difference in stability or instability between spinning containers filled with various levels of water and flat or carbonated Sprite or Pepsi. What I did find is that the amount of water or soft drink placed in the spinning glasses did effect stability, whatever type of liquid was enclosed. I also tried ice cold and room temperature liquids and in all cases it was the way that the glass was spun and the height of the liquid in the container that determined the stability of the spinning volume, not the temperature. From my experiments I can conclude that it is not the carbonation, the temperature or the type of water based drink that causes instability in spinning. In my experiments the physical geometry, the mass of the glass and speed of rotation are what effected the stability of the spinning container and fluid. I believe that the only difference between my experiments and yours must be related to the structure of your glasses relative to mine. Many odd things can happen when masses with odd mass distributions are spun. In these cases it is the speed of rotation that determines stability. Perhaps you can do some experiments to determine where the center of mass of your glasses are located. If the center of mass is not located exactly on the vertical axes of symmetry of your glasses (the spin axis), many odd things can happen when spinning them. It is difficult to believe that a few percent of volume difference and less than 1% of weight difference between carbonated and flat water are key stability factors. The problem is that you indicated that the effect that you observed was independent of the liquid level in the glasses making the variation between carbonated and flat water to be an insignificant factor. Still scratching my head about this question, Your Mad Scientist Adrian Popa
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