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Why arent astrtonauts weightless in space?

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lgski
Posts: 1832 - Karma: 2,291

^ is question number 4 on the phsyics lab im doing right now and i know it has something to do with gravity always being there or somthing. But when i write it down it sounds dumb.

Can anyone provide a super smart sounding answer?

Feb 13 2012 12:21PM
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[evan]
Posts: 5628 - Karma: 117
i thought they were?
Feb 13 2012 12:23PM
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.boz
Posts: 456 - Karma: 192
Haha what?
Feb 13 2012 12:26PM
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fujarome
Posts: 8630 - Karma: 1,561
They are in orbit, so gravity is pulling them down, but they are traveling at speeds higher than earth's escape velocity which means they follow the curvature of the earth as they fall.

...or something like that.


Plus they aren't truly weightless as they still have the same amount of mass as they would on earth.
Feb 13 2012 12:29PM
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blackmamba.
Posts: 969 - Karma: 56
same relative mass. different gravitational pull.

not in science
Feb 13 2012 12:32PM
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E.C.
Posts: 3211 - Karma: 319
this the force pulling you back down is a lot less then on earth but yet mass never changes
Feb 13 2012 12:35PM
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Smuffy
Posts: 4686 - Karma: 3,408
you cant ever be truly weightless. as long as there is another mass somewhere, there will be gravitational attraction. the larger and closer it is, the larger the gravitational pull. essentially...
Feb 13 2012 12:36PM
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Flying~Squirrel
Posts: 6494 - Karma: 192
they are being "pulled on" by earth, the moon, the sun, and every other celestial body in the universe.
Feb 13 2012 12:41PM
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RickAstley
Posts: 953 - Karma: 32
The force of gravity is equal to the Gravitational constant multipled by the mass of the object (astronaut) multiplied by the mass of another object (any random object in the universe divided by the distance between them squared.

Therefore the gravitational field of any object is infinite. No matter where an object is in the universe it will feel the gravitational pull of every single other object in the universe.

Weight is equal to mass times the force of gravity. Therefore, all objects have mass, even if the force of gravity at that point is very small.
Feb 13 2012 12:45PM
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RickAstley
Posts: 953 - Karma: 32
*therefore all objects have weight
Feb 13 2012 12:48PM
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zerospinskier
Posts: 4867 - Karma: 350
That's all you really need to know. Weight = mg, so if there is any g, there is weight.
Feb 13 2012 12:48PM
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paprikapringles
Posts: 106 - Karma: 44
^^ pretty much what he said, i had physics modules at uni cant remember shit but rings a bell :D
Feb 13 2012 12:54PM
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FLBP
Posts: 1794 - Karma: 310
Click for larger image
Feb 13 2012 1:12PM
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I_Am_Mod
Posts: 13214 - Karma: 3,753
they aren't weightless, they're just falling around the earth instead of towards the earth, thats why they appear to be weightless ....
Feb 13 2012 1:33PM
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Lé.Skiing
Posts: 10035 - Karma: 8,128
Poke a hole into the bottom of a paper cup. Covering the hole with your finger, fill it with water. Now hold it above your head and remove your finger. Water will drip out the hole. Drop the cup and watch it fall. While it is falling freely, the water does not drip out. Objects in free fall are weightless.
Feb 13 2012 1:41PM
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lineskier53
Posts: 192 - Karma: 21
That's actually pretty accurate. Gravity is still pulling them down, but they're falling around the Earth instead of towards it. It gives the feeling of weightlessness, but they're essentially in free fall.
Feb 13 2012 2:54PM
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cobra_commander
Posts: 16909 - Karma: 4,687
NO NO NO

They are not 'weightless' the earth is still excerpting a force on them. They are however in an elliptical orbit with velocity components that when at periapsis (closest point to earth). Are perpidicular to their position vector reletive to the center of the earth.

The weight of a body is simply a short way of saying 'the gravitational force on a body by the earth' or more accurately stating 'the effect on a bodies velocity due to the interaction of the earth and the bodies masses'

The equation for the force on the body is (Gm1m2)/r^2. G is the gravitational constant. m1 and m2 the masses of the relevant bodies, and r the distance between the two relevant C.O.M. Make sure you use te right units, and you should get a result in either Newtons (N) or pounds (lb).

Given the relatively large values of the earth's mass and G, you will find that the astronaut's weight is not much less than it is at sea level.

This makes sense when you understand that the sum of forces is equal to the time derivative of the mass velocity product. In this situation we can make the assumption that mass is a scalar and not a function of time. Velocity is a vector and a function of time. It is important to note that velocity is a vector, and that vector is changing either direction, magnitude or both while in orbit.
Feb 13 2012 2:55PM
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lineskier53
Posts: 192 - Karma: 21
Though you are absolutely right, I think he needed something a bit simpler.
Feb 13 2012 2:57PM
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ORDEAL
Posts: 6386 - Karma: 75
Weight is the force of gravity on your mass.
Feb 13 2012 3:49PM
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Mr_Bump
Posts: 689 - Karma: 427
this. weight

^this

weight ≠ mass (ok, unless g=1ms^-2 smartass)

Feb 13 2012 4:05PM
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lgski
Posts: 1832 - Karma: 2,291
I asked my teacher after writing down what fujarome said, he basically said the amount of gravity the earth is putting on you is equal to telhe amount of centrifugal force from your orbit. So you are in equilibrium; appearing weightless
Feb 13 2012 4:11PM
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cobra_commander
Posts: 16909 - Karma: 4,687
Your teacher is a fucking moron if they said that.
Feb 13 2012 7:55PM
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CheddarJack
Posts: 5203 - Karma: 7,380
Click for larger image centrifugal force is imaginary. The correct term would be centripetal force but even then that is not the answer. Unless a mass is in a vacuum (which space is NOT), an object is not weightless. There are always some gravitational forces acting on it because every mass has a gravitational pull and if a mass is not in a vacuum then there are other masses around it.
Feb 13 2012 8:58PM
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Good_Deed
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Click for larger image
Feb 13 2012 8:58PM
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-=---=-=-=-
Posts: 424 - Karma: 7
Mass is the measure of the amount of matter in something.

Weight is the force of gravity on something.
Feb 13 2012 9:02PM
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WestWoods
Posts: 960 - Karma: 414
^^^ This, there is attraction to everything, they aren't always in orbit. yet if they are by their space shuttle or even some distant planet like mars, as little of force it may be, is acting on the astronaut and universe..
Feb 13 2012 9:30PM
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