when does an astronaut float in spece?

In a Dutch science quiz the following question is asked:

When will an astronaut in his spaceship outside the earth's atmosphere
begin to float?
A. When he's far enough away from earth's gravity
B. When his spaceship is hanging exactly between two gravity-fields
C. When he turns off the engine of his spaceship.

I did some searching on the internet and found out that even out of
earth's atmosphere there still is a lot of gravity pulling him back.
Supposing he travels so far that earth's gravity would not pull him back
anymore, there would be lots of other celestial bodies attracting him,
finally making him crash onto the surface of it.

And so, if he would be between two planets (for example), in such a
position that they would pull with the same amount on him, that would be
really floating for him. Still it would be theoretically, because the
planets themselve also move in space, shifting the place of equilibrium
in gravity

I don't believe answer C is right. If he would shut of his engine he
would actually float, but once again different gravity-fields from
surrounding bodies would attract him

Am I right?

Bertje

Bertje wrote:

In a Dutch science quiz the following question is asked:

When will an astronaut in his spaceship outside the earth's atmosphere
begin to float?
A. When he's far enough away from earth's gravity
B. When his spaceship is hanging exactly between two gravity-fields
C. When he turns off the engine of his spaceship.

I don't believe answer C is right. If he would shut of his engine he
would actually float, but once again different gravity-fields from
surrounding bodies would attract him

The answer is C. He would float relative to his enviroment (the space ship)
when they both are falling at the same rate. If the engine is running and
he is outside the ship will leave him. He could grab on to it but then he
would feel a force in the direction of the engine thrust (vector). This is
because the rocket (with him) is accelerating, and it is impossible to
separate acceleration and gravitation.
In addiion C requires that he is free of the friction of the atmosphere.

Both A and B could be right, but it requires some more information (there is
no engine thrust).

As this question is related to the accent phase, C should be right.

Am I right?
If you say C you are.

Bertje

Sincerely
Bjørn Ove

On Fri, 05 Dec 2003 01:24:13 +0100, Bertje wrote:

In a Dutch science quiz the following question is asked:

When will an astronaut in his spaceship outside the earth's atmosphere
begin to float?
A. When he's far enough away from earth's gravity
B. When his spaceship is hanging exactly between two gravity-fields
C. When he turns off the engine of his spaceship.

The answer is C.

The condition of "micro-gravity", "weightlessness", or "free fall" will
occur as soon as the engines are shut down... if the ship as left the
ground.

The "outside the atmosphere" term in the question assures that the ship
has left the ground.

I did some searching on the internet and found out that even out of
earth's atmosphere there still is a lot of gravity pulling him back.
Supposing he travels so far that earth's gravity would not pull him back
anymore, there would be lots of other celestial bodies attracting him,
finally making him crash onto the surface of it.

It's a trick question... in a way... kinda

Other gravitational attractions are irrelevant as far as freefall is
concerned... because the ship will be falling freely.

On the ground gravity tries to drag both astronaut and ship towards
the center of the Earth equally, but the ground holds up the ship,
and the walls of the ship hold up the astronaut.

When the ship lifts off the engines move the ship while he astronaut's
body tries to continue falling downwards due to gravity... but the
astronaut is stopped from falling by the walls of the ship. Thus the
astronaut is pushed upwards by the ship. Accelerated by the ship, to be
precise.

When the engines cease accelerating the ship then the ship ceases
accelerating the astronaut. And when that happens then whatever
gravitational fields are affecting the ship will affect both astronaut
and ship equally. Then the astronaut will be in freefall... along with the
ship... even if the ship has only made it a kilometer above the Earth
before the engines quit and is now falling fast...

Bertje

--
Chuck Stewart
"Anime-style catgirls: Threat? Menace? Or just studying algebra?"

H floats relative to his immediate surroundings, the only term of ref that
would make sense, ehen he and whatever he is in are in free fall.

Not sure how any of the answers can relate to this.

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________
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"Bertje" wrote in message
...
| In a Dutch science quiz the following question is asked:
|
| When will an astronaut in his spaceship outside the earth's atmosphere
| begin to float?
| A. When he's far enough away from earth's gravity
| B. When his spaceship is hanging exactly between two gravity-fields
| C. When he turns off the engine of his spaceship.
|
| I did some searching on the internet and found out that even out of
| earth's atmosphere there still is a lot of gravity pulling him back.
| Supposing he travels so far that earth's gravity would not pull him back
| anymore, there would be lots of other celestial bodies attracting him,
| finally making him crash onto the surface of it.
|
| And so, if he would be between two planets (for example), in such a
| position that they would pull with the same amount on him, that would be
| really floating for him. Still it would be theoretically, because the
| planets themselve also move in space, shifting the place of equilibrium
| in gravity
|
| I don't believe answer C is right. If he would shut of his engine he
| would actually float, but once again different gravity-fields from
| surrounding bodies would attract him
|
| Am I right?
|
| Bertje
|


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One other example is the old swinging of a bucket of water attached to a rope. If you
take a photograph of the bucket at the top of the circle, the water is upside down,
which is clearly impossible.....or is it?

If a friend on a ladder catches the bucket, the water will fall out. If a space
traveler stops....guess what......down they go. I suppose this analogy should at
least dispel the idea that two gravitational fields need to be balanced, or the idea
that moving far from the Earth is necessary.

Bertje writes:

In a Dutch science quiz the following question is asked:

When will an astronaut in his spaceship outside the earth's atmosphere
begin to float?
A. When he's far enough away from earth's gravity
B. When his spaceship is hanging exactly between two gravity-fields
C. When he turns off the engine of his spaceship.

C. This is because he is in "free fall". This is, even though
earth's gravity is pulling on him, it's also pulling on his spaceship
causing the same (or very nearly so) acceleration.



I don't believe answer C is right. If he would shut of his engine he
would actually float, but once again different gravity-fields from
surrounding bodies would attract him

Doesn't matter. The different gravity fields attract the spacecraft
with the same acceleration. They accelerate in the same direction at
the same rate, so the astronaut appears to float in the frame of
reference of the spacecraft. In the frame of reference of the earth,
they are both "falling" around the earth in a path called an orbit.

Time to re-read Newton's laws of motion and how they relate to
orbits.

http://galileoandeinstein.physics.vi.../newtongl.html

Jeff
--
Remove "no" and "spam" from email address to reply.
If it says "This is not spam!", it's surely a lie.

"Bertje" wrote in message
...
In a Dutch science quiz the following question is asked:

When will an astronaut in his spaceship outside the earth's atmosphere
begin to float?
A. When he's far enough away from earth's gravity
B. When his spaceship is hanging exactly between two gravity-fields
C. When he turns off the engine of his spaceship.


"weightlessness" or "zero g" or "freefall" occurs when an object is
travelling around a body such that the gravitational pull downwwards is
exactly offset by the ship's velocity. So what happens is that you are
constantly being pulled downwards, but your velocity (at a right angle away
from the body you're orbiting) keeps you exactly the same distance from the
body.

--
Terrell Miller


"Very often, a 'free' feedstock will still lead to a very expensive system.
One that is quite likely noncompetitive"
- Don Lancaster