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Member (Idle past 5937 days) Posts: 3435 From: Edmonton Alberta Canada Joined: |
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Author | Topic: The limitations of common sense | |||||||||||||||||||||||
DominionSeraph Member (Idle past 4783 days) Posts: 365 From: on High Joined: |
sidelined writes: Did you know. though, that the use of the term velocity in escape velocity is not quite correct? It's a label, so whether it's correct depends on what it's describing.
sidelined writes: Really? Would you care to tell us how that works?Since the earth is a soid mass it is understandable that it wold move as a unit. However, air and water are both fluid, and thus would seem to not be likely to flow in the same way due to their "viscosity". Why does the air and ocean travel as though,they too,were solid? Friction and inertia. They're already travelling along with the Earth, so their inertia keeps them going. Any energy lost is made up by friction with the crust. Here: Let's magically reverse the direction of rotation, but leave the water and air alone. What would happen? Well, because of the water and air's inertia, they would keep going. So, around the equator, you'd be hit by winds of 2000mph. The oceans would also be going 2000mph relative to the crust, so they'd crash into and move over the continents.Let's follow the Pacific Ocean: The Pacific would wash over North and South America. Then it would move into the now empty Atlantic basin (the Atlanic ocean being on the other side of Africa and into Asia.) The Pacific would then follow the Atlantic's path of destruction -- washing up and over Africa and Europe. Now, would this west to east movement continue forever? The water moving down into the oceanic basins, then crashing into the contintinential shelves, and then moving up and over the continents? Of course not. Every time an ocean hits a continental shelf, it'll impart a ton of its energy into the crust, slowing both the water and the crust down some. It'll impart some more just as it flows over the earth. Also, the flow would be turbulent as hell, so you'd lose a lot of energy just to friction between water molecules. The oceans would start moving east to west pretty quickly. The ocean of air would take a bit longer, but that's it.
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
The water moving down into the oceanic basins, then crashing into the contintinential shelves, and then moving up and over the continents? Of course not. Every time an ocean hits a continental shelf, it'll impart a ton of its energy into the crust, slowing both the water and the crust down some. Here's a common sense conundrum for you: could tides change the orbit of the moon? Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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petrophysics1 Inactive Member |
quote:
-------------------------------------------------------------------------------- If that were always true then panning for gold wouldn't work -------------------------------------------------------------------------------- "How does that affect gold panning? As far as my common sense tells me, that rule holds true always. The only reason two objects might fall at different speeds would be a difference in the surface area/weight ratio."Drewsky Unlike everyone else posting here I have no expierence dropping two different objects in a vacuum. If you take a gold nugget and a similar sized piece of quartz and drop them both at the same time in an aquarium filled with water, you will see that the gold hits the bottom much faster than the quartz. If you do this with gold and wood in water, you will further notice that the while the gold goes down the wood goes up. This has nothing to do with inertia, hydraulics, or the Brazil Nut effect. Gold drops much faster in water than the minerals it is commonly found with in a placer deposit, and that is the reason the various placer mining techniques work and concentrate the gold. Understanding this will make you a much better placer gold prospector and miner. You can take that to the bank from someone who has spent his spare time doing it for over 30 years and buys his placer mining equipement from Keene Engineering. Common sense is the result of observation and doing in the real world and for sure makes taking Physics 101 easier. However, I am not sure that taking Physics 101 leads to an increase in common sense.
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tsig Member (Idle past 2938 days) Posts: 738 From: USA Joined: |
Nothing sharpens the statistical sense like a busted straight and a called bluff Sounds more like betting on the come, than bluffing.
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
Sounds more like betting on the come, than bluffing. The poker terminology for it is 'semi-bluff'. Common sense gets a lot of poker things very wrong and I have a lot to thank David Sklansky for ridding me of my intuition and giving me a new one
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sidelined Member (Idle past 5937 days) Posts: 3435 From: Edmonton Alberta Canada Joined: |
DominionSeraph
sidelined writes:
Really? Would you care to tell us how that works?Since the earth is a soid mass it is understandable that it wold move as a unit. However, air and water are both fluid, and thus would seem to not be likely to flow in the same way due to their "viscosity". Why does the air and ocean travel as though,they too,were solid? Friction and inertia. They're already travelling along with the Earth, so their inertia keeps them going. Any energy lost is made up by friction with the crust. This does not explain why the air is already travelling along with the earth. Friction with the crust cannot explain why the atmosphere above the contact with crust also moves along. The issue on the escape velocity is simply that velocity is a vector measurement that includes direction and escape velocity is independent of direction.
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sidelined Member (Idle past 5937 days) Posts: 3435 From: Edmonton Alberta Canada Joined: |
petrophysics
sidelined writes: "We can investigate further as Galileo and others did to arrive at the notion that objects of different masses fall to earth with the same acceleration." petrophysics writes: If that were always true then panning for gold wouldn't work. Of course it can since in the gold panning you are not removing the force of electromagnetism present in the water which provides the resistance to motion. For that same reason, in air, a feather and a lead ball also fall at different rates. The acceleration due to gravity is still the same. It is merely overpowered by the electromagnetic force.
In firing large artillary rounds, the rotation of the earth is taken into account
That is correct. However,the acceleration due to gravity is still independent of the motion of the earth.
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petrophysics1 Inactive Member |
Let's see.
Force=ma What are the forces acting on an object in water? 1. The Force of gravity(Fg)2. The force of buoyancy(Fb) These are vectors, Fb is positive, Fg is negative Therefore: Fb + (-Fg)= ma Fb/m + (-Fg)/m = a Are you seriously suggesting that "a" is always equal to -9.8m/sec^2 ? Now what I just explained accounts for gold falling much faster in water than things with a lower specific gravity. It also explains why wood when released in water goes up.
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DominionSeraph Member (Idle past 4783 days) Posts: 365 From: on High Joined: |
RAZD writes: Here's a common sense conundrum for you: could tides change the orbit of the moon? Well, I know that's the explanation used for its retreat, but I haven't a clue as to how it works.
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DominionSeraph Member (Idle past 4783 days) Posts: 365 From: on High Joined: |
sidelined writes: Friction with the crust cannot explain why the atmosphere above the contact with crust also moves along. Air moves into and out of the boundary layer due to cooling/heating.
sidelined writes: The issue on the escape velocity is simply that velocity is a vector measurement that includes direction and escape velocity is independent of direction. Assuming your starting point isn't on a rotating body.
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
cavediver writes: (as two birthdays a day apart only restricts 5 days from the calendar, not 6) Now you're getting into the fuzzy math area and the assumed definitions in the original question (that "the same day" is a specific 24 hour period and not just within 24 hours of each other). To be consistent you would have to block out 72 hour periods and lump all people into those periods, but that isn't the same as birthday +/-1 day ... This shows how restating the problem can also help avoid making a logical error. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
sidelined, msg 45 writes: But what is it that allows us to differentiate between this as a consequence of a planet rotating on its axis and one that is not? It would seem that the same situation is present in either scenario. That is why being near the earth is not going to tell us much. You have to launch the cannonball high enough for the difference between the rotational speed of the earth and the horizontal speed of the ball to be significantly different. The difference in lag between the two examples I gave points to a test: many simultaneous launches to different heights and tracking where they land. Do it on days with winds in different directions -- to eliminate the effect of winds -- and a clear pattern should emerge one way or the other. This message has been edited by RAZD, 04*12*2006 08:07 PM we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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RAZD Member (Idle past 1434 days) Posts: 20714 From: the other end of the sidewalk Joined: |
DominionSeraph writes: sidelined writes: The issue on the escape velocity is simply that velocity is a vector measurement that includes direction and escape velocity is independent of direction. Assuming your starting point isn't on a rotating body. Launch two rockets at the same time, one for normal orbit and one for retrograde orbit. Design them so that the just go into orbit once all the way around the earth based on non-rotating earth. Launch them from Panama or an island in the middle of the Pacific you give you lots of water to land in. Will they:
Remember that the earth continues to turn after the launch in the rotating earth theory ... Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
... to learn ... to think ... to live ... to laugh ... to share.
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Dubious Drewski Member (Idle past 2560 days) Posts: 73 From: Alberta Joined: |
I know what I'm talking about, I am just terrible at English, hehe.
"We can investigate further as Galileo and others did to arrive at the notion that objects of different masses fall to earth with the same acceleration." That is true ALWAYS. When you observe two objects falling at different rates, it's only because the weight-to-friction ratio is different for each. Don't you remember the Apollo 15 experiment?
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DominionSeraph Member (Idle past 4783 days) Posts: 365 From: on High Joined: |
RAZD writes: Launch two rockets at the same time, one for normal orbit and one for retrograde orbit. Design them so that the just go into orbit once all the way around the earth based on non-rotating earth. How long's the burn?Also, are you disallowing aerobraking? I mean, you could put it in a highly elliptical orbit with it entering the atmosphere at its first perigee -- slowing it enough to plunk it down at your starting point. With this, the +1000mph for the eastbound and -1000mph for the westbound would have a huge effect, since the eastbound one would miss the atmosphere at perigee, and the westbound one would impact the Earth.
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