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Looking for an intelligent argument. (Terminal Velocity)

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Rig Navigator

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Re: Looking for an intelligent argument.
« Reply #660 on: August 30, 2008, 03:20:06 AM »
Quote from: Matrix on August 30, 2008, 03:14:15 AM
Wake me up when someone wins...

You're going to be Rip Van Winkle then. ;)
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Dr Matrix

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Re: Looking for an intelligent argument.
« Reply #661 on: August 30, 2008, 03:22:40 AM »
Quote from: Rig Navigator on August 30, 2008, 03:20:06 AM
You're going to be Rip Van Winkle then. ;)

Huh? What? I'm for King George!

That's still right, right?
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #662 on: August 30, 2008, 07:12:24 AM »
Quote from: cbarnett97 on August 30, 2008, 01:12:03 AM
it is not relative to anything though
It's relative to the earth.  :-\

Quote
after we figure out the acceleration of the object then we can relate that to the acceleration of the earth
So why are you solving for a known?
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #663 on: August 30, 2008, 02:41:01 PM »
Quote from: TheEngineer on August 30, 2008, 07:12:24 AM
Quote from: cbarnett97 on August 30, 2008, 01:12:03 AM
it is not relative to anything though
It's relative to the earth.  :-\

It is not relative to anything, that is like saying i measured my velocity at 60mph by looking at the freeway, then measure it at 500mph by looking at aircraft then measuring it stationary by looking at a building, which one is right?
Quote from: cbarnett97 on August 30, 2008, 01:12:03 AM
after we figure out the acceleration of the object then we can relate that to the acceleration of the earth
Quote from: TheEngineer on August 30, 2008, 07:12:24 AM
So why are you solving for a known?
what known am I solving for?
« Last Edit: August 30, 2008, 02:43:29 PM by cbarnett97 »
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #664 on: August 30, 2008, 02:48:29 PM »
Quote from: cbarnett97 on August 30, 2008, 02:41:01 PM
It is not relative to anything, that is like saying i measured my velocity at 60mph by looking at the freeway, then measure it at 500mph by looking at aircraft then measuring it stationary by looking at a building, which one is right?
They are all right.  Before this goes on any longer, what is the definition of terminal velocity?

Quote
what known am I solving for?
Acceleration.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #665 on: August 30, 2008, 02:55:51 PM »
Quote from: TheEngineer on August 30, 2008, 02:48:29 PM
Quote from: cbarnett97 on August 30, 2008, 02:41:01 PM
It is not relative to anything, that is like saying i measured my velocity at 60mph by looking at the freeway, then measure it at 500mph by looking at aircraft then measuring it stationary by looking at a building, which one is right?
They are all right.  Before this goes on any longer, what is the definition of terminal velocity?

Quote
what known am I solving for?
Acceleration.
since they are all right I choose a FoR that shows that the earth is accelerating less and less which shows that we can not be accelerating at 9.8m/s/s congrats you just proved the earth can not be accelerating.
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #666 on: August 30, 2008, 03:04:40 PM »
What?
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #667 on: August 30, 2008, 03:17:45 PM »
let us take a step back then.

A person is flown to an altitude above the earth that is totally covered by clouds and given an accelerometer and an airspeed indicator and he jumps out of the plane to determine the model. so when he jumps out he notices that the accelerometer shows an acceleration of 9.81m/s/s then it gradually goes to zero while his airspeed increases then remains static, so now he must ask himself either a) he was accelerated down while air resistance counteracted that until he reached a state of equalibrium or b) he remained stationary until the force from air resistance accelerated him up until he reached a state of equalibrium. from there he would need to test to see which one is correct. And as you can see at no time can that person relate what is happening to him with the surface of the earth. the acceleration of the earth is not in this system only the velocity of the air.
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #668 on: August 30, 2008, 05:00:00 PM »
Quote from: cbarnett97 on August 30, 2008, 03:17:45 PM
And as you can see at no time can that person relate what is happening to him with the surface of the earth.
So?  He will still reach a terminal velocity.
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #669 on: August 30, 2008, 05:13:07 PM »
Quote from: TheEngineer on August 30, 2008, 02:48:29 PM
Quote
what known am I solving for?
Acceleration.
You seem to have missed this part.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #670 on: August 30, 2008, 05:17:09 PM »
Quote from: TheEngineer on August 30, 2008, 05:00:00 PM
Quote from: cbarnett97 on August 30, 2008, 03:17:45 PM
And as you can see at no time can that person relate what is happening to him with the surface of the earth.
So?  He will still reach a terminal velocity.
relative to the air not to the surface of the earth, which is why it takes longer to reach his terminal acceleration
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #671 on: August 30, 2008, 05:23:52 PM »
I've already shown that to be untrue.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #672 on: August 30, 2008, 05:31:54 PM »
Quote from: TheEngineer on August 30, 2008, 05:23:52 PM
I've already shown that to be untrue.
I can do math incorectly also to "prove" things but that does not mean that it is true
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #673 on: August 30, 2008, 05:36:55 PM »
Well, my math is correct.  I've posted it for you to disprove, but you have still failed to do so. 
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #674 on: August 30, 2008, 05:49:02 PM »
Quote from: TheEngineer on August 30, 2008, 05:36:55 PM
Well, my math is correct.  I've posted it for you to disprove, but you have still failed to do so. 
I have shown you many times and every time it is shown to you, you just ignore it so go back and read through the posts and you will find many examples of how your math is wrong
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #675 on: August 30, 2008, 05:53:31 PM »
You've stated that I am solving for a known.  I am not.  You claimed one equation was wrong.  It was not.  Your examples are meaningless without support.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #676 on: August 30, 2008, 06:20:07 PM »
v=aeartht is somehow not known?
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #677 on: August 30, 2008, 06:44:10 PM »
Terminal velocity is not known.  Which is what we are solving for.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #678 on: August 30, 2008, 06:47:57 PM »
Quote from: TheEngineer on August 30, 2008, 06:44:10 PM
Terminal velocity is not known.  Which is what we are solving for.
so you take a known and somehow turn it into an unknown? or do you put a new velocity into the equation
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #679 on: August 30, 2008, 07:15:58 PM »
Terminal velocity is not known.  And it remains that way until we solve for it.  Then it becomes a known.
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Parsifal

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Re: Looking for an intelligent argument.
« Reply #680 on: August 30, 2008, 08:53:41 PM »
Quote from: cbarnett97 on August 30, 2008, 02:55:51 PM
since they are all right I choose a FoR that shows that the earth is accelerating less and less which shows that we can not be accelerating at 9.8m/s/s congrats you just proved the earth can not be accelerating.
Quote from: TheEngineer on August 30, 2008, 03:04:40 PM
What?

This is my favourite part.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #681 on: August 30, 2008, 09:07:48 PM »
Quote from: TheEngineer on August 30, 2008, 07:15:58 PM
Terminal velocity is not known.  And it remains that way until we solve for it.  Then it becomes a known.
so you aolved for the accleration of the object first then related that to the earth could you show all that math because it lookes like you just copied the derivation for the RE model.
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #682 on: August 30, 2008, 09:09:02 PM »
Quote from: TheEngineer on August 28, 2008, 09:35:10 PM


Quote from: TheEngineer on August 21, 2008, 09:53:44 AM
The drag force on a body in a fluid is given by
 
F = .5*Cd*v2*A*rho                                                       (1)

where Cd is the drag coefficient, v is the velocity of the object, A is the cross sectional area of the object and rho is the density of the fluid.

We know from Newton's Second Law of Motion that

F = m*ao                                                                      (2)

where F is force, m is the mass of the object and ao is the acceleration of the object.  Rearranging (2) gives us

ao = F/m                                                                       (3)

Combining (3) and (1) gives

ao = Cd*v2*A*rho/(2*m)                                                 (4)

Now, an object that has reached terminal velocity, vt, has no relative acceleration to the Earth.  Applying this to the FE, that means that the object must have an upwards acceleration equal to that of the Earth's.  It follows then, that

ae - ao = 0                                                                   (5)

where ae is the acceleration of the Earth and ao is the acceleration of the object. 

Rearranging (5) gives

ae = ao                                                                        (6)

which, by examination, is correct for all objects whose height is not changing relative to the Earth (aircraft for example). 

Combining (6) and (4) leaves us with the equation

ae = Cd*vt2*A*rho/(2*m)                                              (7)

Performing simple algebra on (7) yields the equation

vt = sqrt(2*ae*m/(Cd*A*rho)                                          (8)

which can easily been seen to be the exact same equation as the one for the RE, with the exception that ae refers to the acceleration of the Earth and a in the RE equation refers to the acceleration due to gravity.

Using your numbers, we see that the terminal velocity on the FE is 22.1426 m/s.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #683 on: August 30, 2008, 09:14:36 PM »
Quote from: TheEngineer on August 30, 2008, 09:09:02 PM
Quote from: TheEngineer on August 28, 2008, 09:35:10 PM


Quote from: TheEngineer on August 21, 2008, 09:53:44 AM
The drag force on a body in a fluid is given by
 
F = .5*Cd*v2*A*rho                                                       (1)

where Cd is the drag coefficient, v is the velocity of the object, A is the cross sectional area of the object and rho is the density of the fluid.

We know from Newton's Second Law of Motion that

F = m*ao                                                                      (2)

where F is force, m is the mass of the object and ao is the acceleration of the object.  Rearranging (2) gives us

ao = F/m                                                                       (3)

Combining (3) and (1) gives

ao = Cd*v2*A*rho/(2*m)                                                 (4)

Now, an object that has reached terminal velocity, vt, has no relative acceleration to the Earth.  Applying this to the FE, that means that the object must have an upwards acceleration equal to that of the Earth's.  It follows then, that

ae - ao = 0                                                                   (5)

where ae is the acceleration of the Earth and ao is the acceleration of the object. 

Rearranging (5) gives

ae = ao                                                                        (6)

which, by examination, is correct for all objects whose height is not changing relative to the Earth (aircraft for example). 

Combining (6) and (4) leaves us with the equation

ae = Cd*vt2*A*rho/(2*m)                                              (7)

Performing simple algebra on (7) yields the equation

vt = sqrt(2*ae*m/(Cd*A*rho)                                          (8)

which can easily been seen to be the exact same equation as the one for the RE, with the exception that ae refers to the acceleration of the Earth and a in the RE equation refers to the acceleration due to gravity.

Using your numbers, we see that the terminal velocity on the FE is 22.1426 m/s.
as I have said your mistake is in your velocity. you can not just have v there it should be vair-vobject. you are trying to skip steps to make the FE model correct
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #684 on: August 30, 2008, 09:26:33 PM »
Do you know what terminal velocity is?
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cmdshft

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Re: Looking for an intelligent argument.
« Reply #685 on: August 30, 2008, 09:27:07 PM »
Not this shit again...
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #686 on: August 30, 2008, 09:27:47 PM »
I thought it was settled already, too.   :-\
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #687 on: August 30, 2008, 09:31:28 PM »
Quote from: TheEngineer on August 30, 2008, 09:26:33 PM
Do you know what terminal velocity is?
Do you know what the FE model is?
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TheEngineer

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Re: Looking for an intelligent argument.
« Reply #688 on: August 30, 2008, 09:33:33 PM »
Yes, I do.  Now answer my question.
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cbarnett97

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Re: Looking for an intelligent argument.
« Reply #689 on: August 30, 2008, 09:35:18 PM »
Quote from: TheEngineer on August 30, 2008, 09:33:33 PM
Yes, I do.  Now answer my question.
I know exactly what terminal velocity is, the problem is you are trying to relate the velocity of the object to the earth before you calculate the behavior of the object. it is like you are calculating how fast a car can go just by looking at it
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