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 Nov 1st 2017, 12:28 AM #1 Member   Join Date: Feb 2017 Posts: 83 Was newton inspired? Galileo proved that g=9.8m/s^2. He used inclined planes and rolled down balls of different masses all balls came down at the same time so then came newton who proved again that g=9.8m/s^2 this is how. F= ma= G x m x M/r^2. m cancels out and we are left with F= a= G x M/r^2. Plug in the values a= 6.67 x 10^-11 x 5.95 x 10^24 ÷ (6.378 x 10^6 m)^2= 9.8 m/s^2. Now since F= ma= G x m x M/r^2. m cancels out and we are left with F= a= G x M/r^2. So when we equate the 2 formulas we know that g is independent of the mass of the object. This is proved by newton thet g does not depend on mass of the object in this way. Newton proved what Galileo observed. So in short Newtons law of universal gravitation was inspired by Galileo. Is this correct?
Nov 1st 2017, 02:30 AM   #2
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 Originally Posted by avito009 Galileo proved that g=9.8m/s^2. He used inclined planes and rolled down balls of different masses all balls came down at the same time so then came newton who proved again that g=9.8m/s^2 this is how.
I don't believe that's true. That would mean that balls of different sizes roll down in the same amount of time which I recall is incorrect. Balls of different sizes have different moments of rotational inertia which means they won't roll down at the same rate. I'm not 100% certain because I haven't calculated something like that in a long time so you should look that up.

 Originally Posted by avito009 So in short Newtons law of universal gravitation was inspired by Galileo. Is this correct?
Don't know. But it should be easy to find out by doing a search using Google. Give it a whirl.

Nov 1st 2017, 06:04 AM   #3
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Have you looked up Galileo's experiment?

In those days people worked in terms of proportion, not equations as we know know them.

 A piece of wooden moulding or scantling, about 12 cubits long, half a cubit wide, and three finger-breadths thick, was taken; on its edge was cut a channel a little more than one finger in breadth; having made this groove very straight, smooth, and polished, and having lined it with parchment, also as smooth and polished as possible, we rolled along it a hard, smooth, and very round bronze ball. Having placed this board in a sloping position, by lifting one end some one or two cubits above the other, we rolled the ball, as I was just saying, along the channel, noting, in a manner presently to be described, the time required to make the descent. We . . . now rolled the ball only one-quarter the length of the channel; and having measured the time of its descent, we found it precisely one-half of the former. Next we tried other distances, comparing the time for the whole length with that for the half, or with that for two-thirds, or three-fourths, or indeed for any fraction; in such experiments, repeated a full hundred times, we always found that the spaces traversed were to each other as the squares of the times, and this was true for all inclinations of the plane, i.e., of the channel, along which we rolled the ball.3
This lead to some complicated reasoning.

Galileo did deduce a constant of proportionality.

Can you say how this compares to a modern version?

 Nov 1st 2017, 06:33 AM #4 Senior Member     Join Date: Jun 2016 Location: England Posts: 322 On the sholders of Giants. Most (all) scientific advancements are "inspired" by the preceding advancements. If you look at the wider environment of ideas prevalent at the time of any "genius" you will find that all the jigsaw pieces of their "great idea" are floating around loose in the scientific correspondence of the day. The key point is that the "genius" is the one who recognises how these various jigsaw pieces can be put together to make a proper picture. __________________ ~\o/~
Nov 1st 2017, 09:53 AM   #5
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 Originally Posted by Pmb I don't believe that's true. That would mean that balls of different sizes
The original post said "different masses". Why are you assuming that means different sizes?

 roll down in the same amount of time which I recall is incorrect. Balls of different sizes have different moments of rotational inertia which means they won't roll down at the same rate. I'm not 100% certain because I haven't calculated something like that in a long time so you should look that up. Don't know. But it should be easy to find out by doing a search using Google. Give it a whirl.

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