Two Plus Two Older Archives  

Go Back   Two Plus Two Older Archives > Other Topics > Science, Math, and Philosophy

Reply
 
Thread Tools Display Modes
  #1  
Old 12-29-2005, 02:52 AM
Lestat Lestat is offline
Senior Member
 
Join Date: Mar 2005
Posts: 383
Default An embarrassing post

I hate to admit this, but for the longest time I though thrust was air pushing off of air. I thought a rocket blasted off by the massive thrust pushing the rocket away from the ground. As it climbed into the air I assumed air has some density so the rocket now had sufficient momentum to push off the air.

Of course I now realize this is all wrong. Thrust has nothing to do with "pushing" as in a water rocket. But I honestly still don't get it. I know that every action has an equal and opposite reaction, but I can't grasp what thrust uses for its opposing force if not the ground or air?

I've tried researching this on the web, but everything I've found is technically beyond me. Is there a thrust or aviation book for dummies? A physics for dummies would be a great book! I love this stuff, but it's beyond my grasp. Don't get me started on after-burners. It gets real ugly. It sucks to be uneducated.
Reply With Quote
  #2  
Old 12-29-2005, 03:00 AM
Guest
 
Posts: n/a
Default Re: An embarrassing post

Conservation of momentum.

http://www.howstuffworks.com/rocket1.htm
Reply With Quote
  #3  
Old 12-29-2005, 03:07 AM
uuDevil uuDevil is offline
Senior Member
 
Join Date: Jul 2003
Location: Remembering P. Tillman
Posts: 246
Default Re: An embarrassing post

In a pressurized, closed container, air pushes on the inside surfaces of the container. If you put a hole in the side, air no longer pushes on the missing area (the hole), so there is an imbalance of forces. This pushes the container (rocket) in the direction opposite that of the hole (nozzle) out of which gas is escaping. The rocket pushes against itself!
Reply With Quote
  #4  
Old 12-29-2005, 03:10 AM
Lestat Lestat is offline
Senior Member
 
Join Date: Mar 2005
Posts: 383
Default Re: An embarrassing post

Whoa! Thanks!!! That's exactly what I was looking for! It even stated that thrust is hard to grasp, so I don't feel quite as dumb. That's definitely a site that will go in my bookmarks. Thanks again!
Reply With Quote
  #5  
Old 12-29-2005, 03:36 AM
daryn daryn is offline
Senior Member
 
Join Date: Apr 2003
Location: Boston, MA
Posts: 2,759
Default Re: An embarrassing post

[ QUOTE ]
In a pressurized, closed container, air pushes on the inside surfaces of the container. If you put a hole in the side, air no longer pushes on the missing area (the hole), so there is an imbalance of forces. This pushes the container (rocket) in the direction opposite that of the hole (nozzle) out of which gas is escaping. The rocket pushes against itself!

[/ QUOTE ]

well, it pushes on the fuel
Reply With Quote
  #6  
Old 12-29-2005, 03:54 AM
Guest
 
Posts: n/a
Default Re: An embarrassing post

Reply With Quote
  #7  
Old 12-29-2005, 04:30 AM
uuDevil uuDevil is offline
Senior Member
 
Join Date: Jul 2003
Location: Remembering P. Tillman
Posts: 246
Default Re: An embarrassing post

[ QUOTE ]
[ QUOTE ]
In a pressurized, closed container, air pushes on the inside surfaces of the container. If you put a hole in the side, air no longer pushes on the missing area (the hole), so there is an imbalance of forces. This pushes the container (rocket) in the direction opposite that of the hole (nozzle) out of which gas is escaping. The rocket pushes against itself!

[/ QUOTE ]

well, it pushes on the fuel

[/ QUOTE ]

Yeah, ok. It just seems more natural to me to consider the fuel to be part of the rocket. If we think of them as separate, then the fuel and the rocket push against each other.
Reply With Quote
  #8  
Old 12-29-2005, 01:00 PM
BluffTHIS! BluffTHIS! is offline
Senior Member
 
Join Date: Nov 2004
Posts: 375
Default Re: An embarrassing post

Post this in OOT and you'll get some different definitions of thrust than given here so far.
Reply With Quote
  #9  
Old 12-29-2005, 01:48 PM
Lestat Lestat is offline
Senior Member
 
Join Date: Mar 2005
Posts: 383
Default Re: An embarrassing post

LOL- That's one reason why I banned myself over there.
Reply With Quote
  #10  
Old 12-29-2005, 09:22 PM
Guest
 
Posts: n/a
Default Re: An embarrassing post

In Wikepedia under "The New York Times" I found this famous mistake:

Famous mistakes
In 1920, a New York Times editorial ridiculed Robert Goddard and his claim that a rocket would work in space:

That Professor Goddard, with his "chair" in Clark College and the countenancing of the Smithsonian Institution, does not know the relation of action to reaction, and of the need to have something better than a vacuum against which to react to say that would be absurd. Of course he only seems to lack the knowledge ladled out daily in high schools
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 07:36 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.