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Originally Posted by nutant gene 71
Exactly! So what is Jupiter's "kilograms" per my bold? Is 100 kg on Earth still 100 kg on Jupiter, in (assumed) 5 G?
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Yes. Kilograms are a unit of measure indicating the amount of matter that an object is composed of. The amount of matter making up the object has not changed.
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Originally Posted by nutant gene 71
Or is it this same mass now 20 "kg" per Jupiter's 5X (Earth) G?
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No.
W = 20kg * 23m/s^2 = 460N which is
NOT what we would observe, if we were wrong about G at Jupiter.
Do the math, and post the calculations step-by-step (you won't do this). Start with Jupiter's mass based on the currently accepted value for G and calculate "g" for Jupiter. Then, replace the currently accepted value of G with any value you choose.
Recalculate Jupiter's mass utilizing this new value of G and then recalculate "g". Since GM remains the same, you will find that "g" is the same.
"g" and the mass of the object you are weighing are all you need to determine weight, since "g" is calculated using G.
You do not need to change the definition of kilograms to support variable G. You will never realize this until you actually sit down, take a deep breath, and work through the calculations step by step. You are trying to take shortcuts, and you are making mistakes. For example:
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So if you weigh on earth 100 kg (Earth scale), your weight on Earth (at 9.8 m/s^2) is 980 N. If G is 5 times greater on Jupiter, your Jupiter weight woud be five times Earth’s N (times 23 m/s^2), so you would weigh 23 * 4900 N, which now makes you in Newtons force = 112,700 N.
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You are saying that W(Jupiter) is W(Earth) * 5 * g(Jupiter). This is just horrendously wrong. In the real, constant G universe, you don't multiply W(earth) by g(Jupiter) to get W(Jupiter). You multiply the mass of the object by the "g" of the planet you are weighing it on. You further mangle the issue by multiplying by the increase in G, which also makes no sense, since g(Jupiter) already includes G (old or "new").
Again, I suggest you work out the calculations with real numbers, starting with the currently accepted values for G and Jupiter's mass. If you just do this, you will see why variable G works just fine (mathematically...) in all regards with the current definition of "kilogram".
Edit to add: if you do the calculations the value for "g" at Jupiter should be closer to 25m/s^2, which is Jupiter's "surface gravity". On the
fact sheet, "surface acceleration" (which for Jupiter is listed at around 23m/s^2) includes the effects of the rotation of the planet.