Aces High Bulletin Board
General Forums => The O' Club => Topic started by: vorticon on January 05, 2005, 10:24:42 PM
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luckily not related to relativity, so i should be able to get a pretty straight answer for once...
if you taka bar of iron and a bar of aluminium and drop them, they will strike the ground at the same time. BUT if you attach them, the iron bar will always strike first. why?
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the aerodynamic drag resultant is at the joint of the 2 bars. the weight resultant is somewher eon the iron bar (iron more dense than aluminum). when you have two forces that act on a body but not at the same point, a turning moment is created.
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How are they attached? If side by side, it would be because the iron is heavier than aluminum.
Its the same as taking a barbell bar and some weight and dropping it.
Once with equal distribution, and once with more weight on one side. The heavier side will fall first.
If you drop the bars separated, gravity is the only force pushing them down. When you combine them, you add the fact of weight distribution (not the right terminology) and inertia
I dont know the actual word for it, but its something along those lines.
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k got it, basicly its a see-saw dealy, heavier side swings down and stays there. just have to forget about gravity as its non relevant to the question.
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neah it only happens in the air.
and come to think of it, the aluminum bar will fall slower than the iron bar in air!
in vacuum, the joint bar will fall straight.
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Wrong, ladies. The only way it will happen that the iron lands below the aluminum, attached or not, is if the bars are big enough for air resistance to come into play.
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thanks for reposting what I just said :D
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Yep, you had it right.
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Originally posted by Lizking
Wrong, ladies. The only way it will happen that the iron lands below the aluminum, attached or not, is if the bars are big enough for air resistance to come into play.
they have exactly the same shape and dimension. air resistance would be about the same
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Originally posted by vorticon
they have exactly the same shape and dimension. air resistance would be about the same
But the centre of mass would not be in the geometric centre of the object (because the iron bar is more dense), thus the application of air resistance (mostly a feature of the geometry of the object) would create a turning moment causing the iron part of the object to end up downwards (assuming the object fell long enough to have time to turn). Of course this assumes a uniform object: if one bar was a significant different shape the turning moment might be different.
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i am imagining 2 "rods" attached down the length, to make a"double rod" say each has i diameter of 1" and length of 2'
dropping so the profile looks liek 2 oo's....
dont forget to account for the air resistance, the alumium bar has less mass and the air comming up will effect it more than the more massive and "stable" iron, hence the aluminium will slow more slowlyin relation to the iron.
i am BAD at explaining it, but i was taught it, and understand the conpect, just can't verbalize it in a drunken hze.
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Originally posted by JB73
i am imagining 2 "rods" attached down the length, to make a"double rod" say each has i diameter of 1" and length of 2'
dropping so the profile looks liek 2 oo's....
dont forget to account for the air resistance, the alumium bar has less mass and the air comming up will effect it more than the more massive and "stable" iron, hence the aluminium will slow more slowlyin relation to the iron.
i am BAD at explaining it, but i was taught it, and understand the conpect, just can't verbalize it in a drunken hze.
Physics and alcohol don't mix! Not that that stopped me at Uni........
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Seeing you use aluminium and iron as an example, would the pull of the Earth's magnetic field play a part in this at all?
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the two variables determining terminal velocity in an atmosphere are density & shape coefficient
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well if you attach a the to bars by they`re tips then then as the new bar (which built of the two bars) accellrate on his way down horizontally will be forced by the drag to change position to a more aerodynamic state since the iron end is heavier it will be effected less by the drag force while the other end will be effected more by it cousing the bar to spin until the iron end pointing down in a more aerodynamic way.
on the other hand if you just drop them separated from each other each bar will land on his own tip.
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Originally posted by Bluedog
Seeing you use aluminium and iron as an example, would the pull of the Earth's magnetic field play a part in this at all?
Yea, that`s what I was wondering.
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you are all wrong.
everyone knows that cats are made of iron.
duh.
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The Iron hits first becuase it has more weight than the aluminum.. Weight being the gravitational force on any given object.
Look at your periodic chart:
Iron (Fe) is number 26
Aluminum (Al) is number 13...
More atomic mass = more weight when a constant gravitational force is applied (earth gravity)
given equal diminsions of the bars the iron is heavier than aluminum and hence the heavier object will shift the center of gravity of the two bars together with the iron falling first.. (given enough distance to complete its rotation)
Note this is "not" (typo edited for scholz sorry bub) in a perfect enviroment such as a vacuum with out any wind/air resistance but could be mimiced in a non vacuum enviroment with similiar results as long as the outside stimulii was equally applied to both bars..
while the magnetic force will have effect on both the iron and the aluminum the force is not powerful enough to interfere with the forces of gravity on planet earth in this scenario..
DoctorYo
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Is it an African or European bar..?
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both objects are together... if you read his initial description of his experiment you would see that..
He already stated :
f you taka bar of iron and a bar of aluminium and drop them, they will strike the ground at the same time.
;)
DoctorYo
if your going to rebuttal me at least read first.. Read the chess suggestion where T0J0 tells me yahoo is for beginers and I already stated a more advanced place to play in a un edited message.. read people read.. it helps..
:lol
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It's not a question of where 'e grips it! It's a simple question of
weight ratios! A Aluminum bar could *not* carry a Iron bar!
:D
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Listen. In order to maintain air-speed velocity, a Aluminum bar needs to vibrate forty-three times every second, right?
Please...
Am I right?
But then of course, Aluminum/Iron bars are non-migratory.
Oh yeah...
:D
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lololololol
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Helium Ballons fall?
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the earth's most powerful vacuum is in between GS's ears just south of his nose, so I'll grant him the expertise on this one. :D
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OK, what if the bars were really strings, like really really long, thin, elongated bars? What if you had an aluminum string say, 6 miles long, and an iron string, 6 miles long, about the thickness of strong thread? And, you tied the strings together. What then. Would it be different if you tied them at the ends? What about if you tied them so that they formed a circle? Would it then make a difference if you dropped them flat, like a pancake, or would you want to drop them on the edge, like a tire?
Tom
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Originally posted by vorticon
if you taka bar of iron and a bar of aluminium and drop them, they will strike the ground at the same time.
Ah, no they wont. You guys are saing that air resistance will cuse the iron bar to hit the grouwnd first if they are attached but magicaly the air resistance does not exist when the bars are not attached?
What ever the material. The heavier bar will hit first.
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Originally posted by dedalos
Ah, no they wont. You guys are saing that air resistance will cuse the iron bar to hit the grouwnd first if they are attached but magicaly the air resistance does not exist when the bars are not attached?
thats exactly what was causing my confusion.
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Heavier objects fall faster than lighter ones (assuming everything else is equal) on Earth.
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Originally posted by SunTracker
Heavier objects fall faster than lighter ones (assuming everything else is equal) on Earth.
Sorry, can't resist..
http://www.nasaexplores.com/show_912_student_st.php?id=040908101213
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Originally posted by dedalos
Ah, no they wont. You guys are saing that air resistance will cuse the iron bar to hit the grouwnd first if they are attached but magicaly the air resistance does not exist when the bars are not attached?
What ever the material. The heavier bar will hit first.
nice troll :rolleyes:
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Sorry, can't resist..
Actually, the objects did fall at different speeds from the Leaning Tower. But they all appeared to land at the same time. If dropped from a greater height, the difference becomes more pronounced (air resistance).
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Air resistance and bouyancy will both cause the less dense end to hit last.
Once the aerodynamic drag cancels the gravitational accelleration terminal velocity is reached. Terminal velocity for two equally shaped objects with different densities will be unequal, the denser object reaching a higher speed.
Bouyancy is a minute force in air but in a heavier fluid could have large consequence.