# helim balloon

sonhouse
Posers and Puzzles 10 Jun '05 16:22
1. sonhouse
Fast and Curious
10 Jun '05 16:22
You are in a space ship, say something the size of the shuttle
external fuel tank, it has a breathable atmosphere.
You very carefully put a balloon filled with helim dead center of the
big room. Then you turn on a rocket that is at one end.
What happens to the balloon? The rocket is giving one G of force
and you are like billions of miles away into space so there is no
gravity when you started.
2. 10 Jun '05 17:07
balloon moves towards the edge in the direction of the G-force
3. 10 Jun '05 17:30
It "rises" away from the G force. If we arbitrarily label the direction of the force as down, the balloon will go up.
4. sonhouse
Fast and Curious
10 Jun '05 19:37
so we have two opposite views here, but which one is correct?
I already know but you guys should be able to figure it out.
5. 10 Jun '05 20:311 edit
Opposite views? We are both stating the same solution. The helium weighs less than the breathable air, and therefor the breathable air will be more inert to the force and therefor push the balloon 'upwards', i.e. in the direction of the force.

edit: when I wrote 'direction of the G-force', it means the direction in which the force is pointing (and not where it comes from). I thought that was obvious.
6. sonhouse
Fast and Curious
10 Jun '05 22:08
Originally posted by Mephisto2
Opposite views? We are both stating the same solution. The helium weighs less than the breathable air, and therefor the breathable air will be more inert to the force and therefor push the balloon 'upwards', i.e. in the direction of the force.

edit: when I wrote 'direction of the G-force', it means the direction in which the force is pointing (and not where it comes from). I thought that was obvious.
Ok, you land the ship on earth right on the rocket, which way does the
helium balloon go? Just seeking clarification. The force in this case
is under your feet towards the ground, is that what you mean?
7. AThousandYoung
11 Jun '05 21:311 edit
Originally posted by Mephisto2
balloon moves towards the edge in the direction of the G-force
balloon moves towards the edge in the direction of the G-force...when I wrote 'direction of the G-force', it means the direction in which the force is pointing (and not where it comes from). I thought that was obvious.

The rocket is giving one G of force

The force (which has a magnitude of G) is acting on the rocket ship, pushing it 'upwards'. It points in the same direction as the acceleration of the rocket ship. The balloon will move in the same direction as the force is acting in.

It "rises" away from the G force. If we arbitrarily label the direction of the force as down, the balloon will go up.

If the force of the rocket is labelled as down, then that means the rocket is accelerating downwards. There will be a 'pseudo gravity' that pushes objects inside the rocket towards the tail. In this case, the balloon will move 'down', because you labelled the direction of the force as down.

I think the problem is is that jebry is considering 'the force' as the 'pseudo gravity' experienced by the people inside, while Mephisto is considering 'the force' as being that exerted by the rocked on the space ship. The latter view is correct; I don't know whether the former is also correct. The definition of 'the force' needs to be clarified.

In the original problem 'the force' is given by the rocket, so I tend to suspect jebry is mistaken. However maybe the problem is that the problem and/or the solution was/were worded unclearly.
8. 12 Jun '05 01:46
If the rocket is accelerating then won't all the air be forced towards the tail end of the rocket by the acceleration which is afterall a force, just like gravity. The helium being lighter will have less weight and therefore be displaced by the heavier 'breathable atmosphere'. So the ballon will rise, just as it would in the Earth's atmosphere.
9. sonhouse
Fast and Curious
12 Jun '05 16:26
Originally posted by jimslyp69
If the rocket is accelerating then won't all the air be forced towards the tail end of the rocket by the acceleration which is afterall a force, just like gravity. The helium being lighter will have less weight and therefore be displaced by the heavier 'breathable atmosphere'. So the ballon will rise, just as it would in the Earth's atmosphere.
you got it! you have to realize what causes the balloon to rise, differance in air density, most dense in the direction of the rocket
and less dense in the other direction, like a watermelon seed squirted
out of your finger, if goes "up", in this case, away from the rocket.
And then the other fact figured out by Einstein is the equivalence of
gravity and acceleration, if you are in a closed box with no instruments
you can't tell if you are in a gravity field or an acceleration field.
Mephisto may have been saying the same thing, it may be just
a matter of semantics.
10. sonhouse
Fast and Curious
12 Jun '05 16:27
Interesting thing is, I posed my little question to physicists and
mechanical engineers who should have known instantly but got it
wrong. Go figure.
11. Bowmann
Non-Subscriber
13 Jun '05 01:30
Originally posted by sonhouse
You are in a space ship, say something the size of the shuttle
external fuel tank, it has a breathable atmosphere.
You very carefully put a balloon filled with helim dead center of the
big room. Then you turn on a rocket that is at one end.
What happens to the balloon? The rocket is giving one G of force
and you are like billions of miles away into space so there is no
gravity when you started.
That depends on what 'helim' is.
12. sonhouse
Fast and Curious
13 Jun '05 18:19
noticed that did youðŸ™‚ Helim
is the more magical version of Helium with ten times the
lifting power and gives out a thousand times the energy
in a fusion reactor.
13. AThousandYoung
14 Jun '05 00:21
Originally posted by sonhouse
Interesting thing is, I posed my little question to physicists and
mechanical engineers who should have known instantly but got it
wrong. Go figure.
Are you sure they got it wrong? You worded the question very ambiguously.
14. 14 Jun '05 01:02
If the helium in the balloon was at a much higher pressure than the surrounding atmosphere it could be denser
15. sonhouse
Fast and Curious
14 Jun '05 14:35
Originally posted by Siskin
If the helium in the balloon was at a much higher pressure than the surrounding atmosphere it could be denser
hell of a balloon though!