Looking for an intelligent argument. (Terminal Velocity)

The accelerating air for the same reason that air slows your acceleration normally, just in reverse.

so the acceleration of the air stops while you are falling?

Personally, I would use the term "resists".

Also jump in the air.  Congrats you followed them without being in free fall. 

Hahaha. When one jumps in the air, one is in freefall until one lands on the ground. Ignoring air resistance, of course.

Your understanding of the FE model is sickening I suggest you learn how to read and then go ahead and show that it is perfectly ok to add items into your equation that do not exist for that system and how you can make a known magically become an unknown and then you can work on the ability to solve something based upon a model instead of trying to force it to fit reality

I'm still waiting for you to use your madd middle skool skilz to show me my error.

Quote from: cbarnett97 on August 21, 2008, 01:49:52 PM

Your understanding of the FE model is sickening I suggest you learn how to read and then go ahead and show that it is perfectly ok to add items into your equation that do not exist for that system and how you can make a known magically become an unknown and then you can work on the ability to solve something based upon a model instead of trying to force it to fit reality

I'm still waiting for you to use your madd middle skool skilz to show me my error.

I am waiting for you to tell me "I need your help because I am unable to properly understand the problem at hand"

Personally, I would use the term "resists".

so 3ft away from you the air is no longer accelerating by you or is the constantly accelerating at 9.81m/s/s which would mean that the velocity of the air is constantly increasing by 9.81m/s/s

The latter.

I am waiting for you to tell me "I need your help because I am unable to properly understand the problem at hand"

I understand it perfectly.  You however, do not.  I have provided you with the derivation of the equation.  It you feel like something is incorrect with it, please address it in the best way you can.  Simply stating, "It is wrong" is not helping your cause.  In fact it is just illustrating your ignorance to everyone. 

The latter.

Now this is where the mistake usually happens, the FE model dictates that when you jump out of an airplane your accleration goes to zero(if you had no air resistance) the only thing that causes your acceleration is this air that accelerates by you.  so you are accelerated in the same direction of the air due to your air resistance, now air resistance is dependent upon you velocity through it so if the velocity of the air is always in creasing the force from air resistance wil always be increasing hence your acceleration up will always be increasing so after a period of time your accleration will be 9.81m/s/s and if we take that and then relate it to the earth you would see that the skydiver would never land if he was high up enough to start with

He would still land because the earth would have more velocity, he would just land slower than without drag.

to quote another member on this forum known for their in depth responses

Uh, no.

Kinda like the pot calling the kettle black

Now this is where the mistake usually happens, the FE model dictates that when you jump out of an airplane your accleration goes to zero(if you had no air resistance) the only thing that causes your acceleration is this air that accelerates by you.  so you are accelerated in the same direction of the air due to your air resistance, now air resistance is dependent upon you velocity through it so if the velocity of the air is always in creasing the force from air resistance wil always be increasing hence your acceleration up will always be increasing so after a period of time your accleration will be 9.81m/s/s and if we take that and then relate it to the earth you would see that the skydiver would never land if he was high up enough to start with

And that is where your mistake is.  Since the skydiver started accelerating from zero and the Earth was accelerating at 9.8m/s^2, the skydiver is going at a slower velocity than the Earth.  Even when the skydiver's acceleration is equal to the Earth's his velocity relative to the Earth's is slower.  Hence the terminal velocity thing.  I hope this illustrates your inability to understand the problem at hand.

Quote from: cbarnett97 on August 21, 2008, 02:08:03 PM

Now this is where the mistake usually happens, the FE model dictates that when you jump out of an airplane your accleration goes to zero(if you had no air resistance) the only thing that causes your acceleration is this air that accelerates by you.  so you are accelerated in the same direction of the air due to your air resistance, now air resistance is dependent upon you velocity through it so if the velocity of the air is always in creasing the force from air resistance wil always be increasing hence your acceleration up will always be increasing so after a period of time your accleration will be 9.81m/s/s and if we take that and then relate it to the earth you would see that the skydiver would never land if he was high up enough to start with

And that is where your mistake is.  Since the skydiver started accelerating from zero and the Earth was accelerating at 9.8m/s^2, the skydiver is going at a slower velocity than the Earth.  Even when the skydiver's acceleration is equal to the Earth's his velocity relative to the Earth's is slower.  Hence the terminal velocity thing.  I hope this illustrates your inability to understand the problem at hand.

model the acceleration of the object and let me know what his acceleration is at t=13

to quote another member on this forum known for their in depth responses

Quote from: TheEngineer on August 16, 2008, 09:24:22 PM

Uh, no.

Kinda like the pot calling the kettle black

I assume this means you can't refute the evidence. 

Figures.

I see where you are trying to go with this, but there is air causing drag above you as well.

I see where you are trying to go with this, but there is air causing drag above you as well.

When you jump out of the plane you're stationary while the earth speeds up towards you correct? Then the air rushing past you must be moving at the same rate as the earth in order for us to feel it's "resistance"?

When you jump out of the plane you're stationary while the earth speeds up towards you correct? Then the air rushing past you must be moving at the same rate as the earth in order for us to feel it's "resistance"?

Yes.

Quote from: Robbyj on August 21, 2008, 02:28:07 PM

I see where you are trying to go with this, but there is air causing drag above you as well.

I'm still waiting for your refutation of my equation.  I even labeled each step for easy reference.  Show me where my mistake is.

In fact, I pose this to everyone:  Is my equation correct?  cbarnett has not really listened to the number of people telling him he has been wrong before, but hey, maybe this time he will. 

Let's get some independent feedback.

See GR.

Back it up; give me a quote from GR that supports your claim that one can follow geodesics without free-fall.

  Also jump in the air.  Congrats you followed them without being in free fall. 

The moment he jumps, the moment he is free-falling in the opposite direction.

Still doesn't mean he is in free fall as he is still not free from external forces. 

Still is, indirectly. He has to follow the geodesics indirectly, due to the mechanical resistance, to stay on the ground.

Quote from: sokarul on August 21, 2008, 01:15:45 PM

See GR.

Back it up; give me a quote from GR that supports your claim that one can follow geodesics without free-fall.

Quote from: sokarul on August 21, 2008, 01:15:45 PM

  Also jump in the air.  Congrats you followed them without being in free fall. 

The moment he jumps, the moment he is free-falling in the opposite direction.

Quote from: Jack. on August 21, 2008, 09:18:30 AM

Still doesn't mean he is in free fall as he is still not free from external forces. 

Still is, indirectly. He has to follow the geodesics indirectly, due to the mechanical resistance, to stay on the ground.

FUCKING LEARN THE DEFINITION OF FREE FALL.

Examples of objects in free fall include:

A spacecraft (in space) with its rockets off (e.g. in a continuous orbit, or going up for some minutes, and then down)
The Moon orbiting around the Earth.
An object dropped in a drop tower for a physics demonstration at NASA's Zero-G Research Facility

Examples of objects not in free fall:

Standing on the ground: the gravitational acceleration is counteracted by the normal force from the ground.
Flying horizontally in an airplane: the wings' lift is also providing an acceleration.
Jumping from an airplane: there is a resistance force provided by the atmosphere.

Quote from: cbarnett97 on August 21, 2008, 05:28:59 AM

Quote from: TheEngineer on August 20, 2008, 12:29:05 AM

Relative to the Earth?  When your upwards acceleration equals the acceleration of the Earth.

But, I've said this already.

Made this using LaTex and I forgot to resize the page so sorry

Your 'FE' equation is wrong.  Since you let us all have a good laugh, I'll go ahead and post the derivation for you.

The drag force on a body in a fluid is given by
 
F = .5*C_d*v²*A*rho                                                       (1)

where C_d 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*a_o                                                                      (2)

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

a_o = F/m                                                                       (3)

Combining (3) and (1) gives

a_o = C_d*v²*A*rho/(2*m)                                                 (4)

Now, an object that has reached terminal velocity, v_t, 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

a_e - a_o = 0                                                                   (5)

where a_e is the acceleration of the Earth and a_o is the acceleration of the object. 

Rearranging (5) gives

a_e = a_o                                                                        (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

a_e = C_d*v_t²*A*rho/(2*m)                                              (7)

Performing simple algebra on (7) yields the equation

v_t = sqrt(2*a_e*m/(Cd*A*rho)                                          (8) <--------This is where you messed up

which can easily been seen to be the exact same equation as the one for the RE, with the exception that a_e 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.



p.s.  Your RE equation is wrong.

And you are right When I ran the math through excel I must have entered it wrong because the Acceleration should be greater than I showed. Also to be more accurate I should have calculated the velocity of the object to relate it to the velocity of the air, I will rerun the numbers maybe tomorrow if I have time, but I am still confident they will show a difference between the 2 models but who knows we will see

Your bold and arrow is nice and all, but you forgot to explain why (8) is wrong.

FUCKING LEARN THE DEFINITION OF FREE FALL.

Says the person who knows nothing about geodesic motion, let alone the mechanics of GR.

Quote

Examples of objects in free fall include:

A spacecraft (in space) with its rockets off (e.g. in a continuous orbit, or going up for some minutes, and then down)
The Moon orbiting around the Earth.
An object dropped in a drop tower for a physics demonstration at NASA's Zero-G Research Facility

Examples of objects not in free fall:

Standing on the ground: the gravitational acceleration is counteracted by the normal force from the ground.
Flying horizontally in an airplane: the wings' lift is also providing an acceleration.
Jumping from an airplane: there is a resistance force provided by the atmosphere.

Then GTFO of Newtonian physics.

Your bold arrow is nice and all, but you forgot to explain why (8) is wrong.

If 7 is right, then 8 is right as well.

Quote from: sokarul on August 21, 2008, 10:06:29 PM

FUCKING LEARN THE DEFINITION OF FREE FALL.

Says the person who knows nothing about geodesic motion, let alone the mechanics of GR.

Quote from: sokarul on August 21, 2008, 10:06:29 PM

Quote

Examples of objects in free fall include:

A spacecraft (in space) with its rockets off (e.g. in a continuous orbit, or going up for some minutes, and then down)
The Moon orbiting around the Earth.
An object dropped in a drop tower for a physics demonstration at NASA's Zero-G Research Facility

Examples of objects not in free fall:

Standing on the ground: the gravitational acceleration is counteracted by the normal force from the ground.
Flying horizontally in an airplane: the wings' lift is also providing an acceleration.
Jumping from an airplane: there is a resistance force provided by the atmosphere.

Quote

Then GTFO of Newtonian physics.

GIVE IT UP.  My pinky finger knows more about GR and SR then you ever will.  This has nothing to do with Newtonian physics.  The proof is right in front of you. 

GIVE IT UP.  My pinky finger knows more about GR and SR then you ever will. 

Yo,

1 = -1

This has nothing to do with Newtonian physics.  The proof is right in front of you. 

It's Newtonian physics (gravitational acceleration counteracted by normal force) and it's not even a proof.

Quote from: sokarul on August 22, 2008, 07:52:47 AM

GIVE IT UP.  My pinky finger knows more about GR and SR then you ever will. 

Yo,

Quote

1 = -1

Quote from: sokarul on August 22, 2008, 07:52:47 AM

This has nothing to do with Newtonian physics.  The proof is right in front of you. 

It's Newtonian physics (gravitational acceleration counteracted by normal force) and it's not even a proof.

That has nothing to do with Newtonian physics.  Also way to copy wiki word for word.  A guy sitting in a chair is not if free fall.  End of story.     

That has nothing to do with Newtonian physics. 

Open your eyes now.

A guy sitting in a chair is not if free fall.  End of story.     

If only you knew some GR. End of story.

Quote from: sokarul on August 22, 2008, 08:13:34 AM

That has nothing to do with Newtonian physics.  Also way to copy wiki word for word.  A guy sitting in a chair is not if free fall.  End of story.     

If only you knew some GR. End of story.

Prove me wrong.  O wait you can't.  Otherwise you would of.  The guy in a chair is neither free of forces or falling.