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Accelerating Up?

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cbarnett97

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Accelerating Up?
« on: June 06, 2007, 11:37:30 PM »
I know it has been gone over in many forms but here is a new angle I think. I the earthe is moving up and that is why it seems like there is gravity then how do parachutes work, because if the ground is coming up to us then a parachute would be totally inefective because the ground would come up to meet us no matter how much wind resistance we created. Now however if we were attracted to the earth through some unseen force such as gravity then a parachute would work because the ground is stationary in the horizontal direction.
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Gulliver

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Re: Accelerating Up?
« Reply #1 on: June 06, 2007, 11:40:15 PM »
Quote from: cbarnett97 on June 06, 2007, 11:37:30 PM
I know it has been gone over in many forms but here is a new angle I think. I the earthe is moving up and that is why it seems like there is gravity then how do parachutes work, because if the ground is coming up to us then a parachute would be totally inefective because the ground would come up to meet us no matter how much wind resistance we created. Now however if we were attracted to the earth through some unseen force such as gravity then a parachute would work because the ground is stationary in the horizontal direction.
No. Sorry. A parachute creates drag that slows the descent of the jumper--in either model.
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cbarnett97

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Re: Accelerating Up?
« Reply #2 on: June 06, 2007, 11:42:02 PM »
But if I understand the FE model correctly there is no descent. we jump up and the earth comes up to meet us we do not fall back down to the earth
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TheEngineer

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Re: Accelerating Up?
« Reply #3 on: June 06, 2007, 11:45:59 PM »
The earth is accelerating the air. 
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cbarnett97

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Re: Accelerating Up?
« Reply #4 on: June 06, 2007, 11:48:49 PM »
if the air is boeing accelerated up as well then when you go skydiving the air should be rushing past you at 9.8m/s^2 but it does not so that would lead me to believe that the air is not accelerating there have been times when there has been nearly zero wind.
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TheEngineer

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Re: Accelerating Up?
« Reply #5 on: June 06, 2007, 11:51:40 PM »
When you go skydiving, the air sure is rushing past you at 9.8m/s^2.  If it was stationary with respect to you, that parachute would not do you much good.
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cbarnett97

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Re: Accelerating Up?
« Reply #6 on: June 06, 2007, 11:55:30 PM »
if the air was rushing past you at 9.8 m/s that would cause you to gain altitude, instead it is moving past you around 1.5 m/s (varies on your weight) which is all that is required to slow your descent. It is a simple pressure problem.
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TheEngineer

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Re: Accelerating Up?
« Reply #7 on: June 07, 2007, 12:00:33 AM »
If the air is stationary with respect to the earth and you are accelerating at 9.8m/s^2 with respect to the earth, then guess what, you are accelerating through the air at the same rate.
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cbarnett97

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Re: Accelerating Up?
« Reply #8 on: June 07, 2007, 12:08:30 AM »
Maybe I am misunderstanding this but if the earthe as well as the air are accelerating up then it seems to me that it would not matterwhat you did to yourself the earth would come to you at the same speed no matter what. it would be the same thing as a car coming at you at 60 mph, it would not matter what you did the car will hit you at the same time as if you did nothing because it is the car that is accelerating not you, while with a parachute you are accelerating toward the earth so that will effect your acceleration
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TheEngineer

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Re: Accelerating Up?
« Reply #9 on: June 07, 2007, 12:10:59 AM »
Look at it like this:

Which will hurt more, being hit by a car that is traveling at 60mph while you are standing on the sidewalk, or you hitting a car that is stationary while you are traveling at 60mph? 

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cbarnett97

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Re: Accelerating Up?
« Reply #10 on: June 07, 2007, 12:18:48 AM »
That would be the same force which would explain jumping out of a plane with no parachute, but it would be more like the car was going 60 mph but then you increased your wind resistance and all of the sudden the car just started going 5 mph, it does not make sense to me.
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TheEngineer

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Re: Accelerating Up?
« Reply #11 on: June 07, 2007, 12:26:02 AM »
The earth is accelerating the air.  When you jump out of the plane, you stop accelerating and continue moving at a constant velocity.  The earth is still accelerating and is doing the same to the air.  So the air is rushing past you.  The force due to drag is low in this configuration, and you accelerate towards the earth rather quickly.  When you open the chute, the drag increases dramatically, thus slowing your approach to the earth.
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cbarnett97

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Re: Accelerating Up?
« Reply #12 on: June 07, 2007, 12:31:13 AM »
That is very true in the RE model. But in the FE model your body does not accelerate you stay where you are and the earth comes to you so the feeling should be the same the entire time. Now I dont know if you have ever skydived before (if you have not you should, its lots of fun) but you go through a period of acceleration that you can feel then you reach your terminal velocity, and your acceleration is essentially zero then you pull your chute and you go through a period of negative acceleration til you reach your new terminal velocity. now if it was indeed the earth that was accelerating up to us our experience would be totally different
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TheEngineer

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Re: Accelerating Up?
« Reply #13 on: June 07, 2007, 12:34:12 AM »
What I explained was the FE version.
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cbarnett97

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Re: Accelerating Up?
« Reply #14 on: June 07, 2007, 12:37:33 AM »
well according to the explanation I read on this site it said "So if you jump, you're temporarily not affected by it, it just quickly pushes the Earth back into you." now somewhere there is a contradiction in the FE Model
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TheEngineer

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Re: Accelerating Up?
« Reply #15 on: June 07, 2007, 12:45:56 AM »
When you are on the ground, you are being accelerated by the earth.  When you jump, you are no longer in contact with the earth, but due to your temporary increase in acceleration due to your jump, you are traveling faster than the earth at that moment, but at a constant velocity.  The earth is still accelerating at 9.8m/s^2, so it takes a short time to catch up to your velocity.

No contradiction at all.
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Bushido

Re: Accelerating Up?
« Reply #16 on: June 07, 2007, 01:53:47 AM »
@ thread. Stop being an ignorant n00b.
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Trekky0623

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Re: Accelerating Up?
« Reply #17 on: June 07, 2007, 05:46:38 AM »
The Earth and the atmosphere are accelerating.  Therefore wind resistance is the air rushing past you.  You would still be able to create wind resistance, you would just have a little acceleration yourself.
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