Movement of Large Objects in Outer-Space

[Gdepp519]

So, a couple of my friends and I were in my basement playing star'trek on the xbox360.. and despite the craptackular graphics... an interesting question was raised..

I noted that wouldn't it be alot easier for heavier objects to move in space??.. because i noticed that within the game it took the starship forever to turn especially if they were big...

And my friend stated that its all relative and that even though there isn't any gravity or any real friction in outer-space the mass of the object is still a factor and thus still makes it difficult for large objects to move

so i just wanted a second opinion on this explanation..

 

[Aimster]

Blah I came in here expecting a thread about aliens attacking earth

 

[letdown427]

Force = Mass x Acceleration if there's no resistance (as I recall?)

I'd assume that yeah, the additional resistance provided by air and things would play a factor, but compared to the force required to accelerate the mass anyway, the difference is probably negligible.

 

[Gdepp519]

well maybe i was asleep during my science class in high school.. when this was explained..

how can i ask this:

So then mass is determined by gravity?? On earth it is because we have a set of standard to measure mass i assume?? How is Mass determined in space then???
If there is no gravity in space how can you figure out how much something weighs?? or does that not even matter?? And we'd just have to worry about mass of an object
we'd move in space??

sorry if im rambling..

 

[0roo0roo]

still requires force to get started, but no friction/air resistance probably does help quite a bit.

 

[Bootprint]

Weight is determined by gravity. You weight less on the moon, then on the earth. But your mass is the same.

 

[Gdepp519]

ahh. so then.. mass is the only constant.. your weight is relative to where you are??

i think that sounds right.. lol

 

[bunnyfubbles]

Larger ships (objects) are going to have larger mass, just because they may be "weightless" in space doesn't mean it won't take a lot more force to change its direction (acceleration) relative to a smaller ship (object) of less mass.

 

[Gdepp519]

cool.. that was simple enough then..

 

[Safeway]

It has to do with inertia.

 

[MrDudeMan]

first of all, there is most definitely gravity in space. tell your friend that is flat out wrong.

secondly, anything with mass has inertia. inertia is resistance to acceleration. an object with more mass will have more inertia, so while there is less friction in deep space, there is still inertial resistance. you cant say it has no resistance because that includes inertia, making it an untrue statement.

the weight of an object with respect to a given reference frame decreases exponentially as it moves away. when you travel away from the earth, you start to become "lighter" with respect to someone on the surface, but you have to go quite a long distance to start feeling the effects. i calculated it once a year or so ago, but IIRC, you have to be 300+ miles away to be 1% lighter.

something else you may find interesting...there is roughly 1 atom per cubic meter in deep space. this means there is essentially zero particle resistance on the exterior of a spaceship. as i said before, the fact that it cant turn instantaneously is almost purely a function of inertia. rotating a large mass around a point in space is no different than doing it on earth if you do it slowly. why is it hard to push a roundabout on a playground even at slow speeds? air resistance is negligible. if more people get on and sit near the outside of the ring it is even harder. ignoring the resistance of the bearings/bushings holding the platform up, it will become harder to push because there is more mass further away from the center of mass, adding inertial resistance.

another thing to help you visualize...if all of the mountains on earth collapsed to sea level, the earth would spin faster. mountains pull the center of mass of the earth away from the geometric center, and all mass not in the center adds inertial resistance.

 

[Gdepp519]

awesome.. thanks alot

are you pulling this info from ur personal knowledge?? or so you know of a website that explains this??

 

[MrDudeMan]

Originally posted by: Gdepp519
awesome.. thanks alot

are you pulling this info from ur personal knowledge?? or so you know of a website that explains this??

i learned all of this from physics books/classes, so off the top of my head. if you want to know more just say the magic words.

 

[Gdepp519]

do share

 

[Paratus]

Originally posted by: MrDudeMan

Originally posted by: Gdepp519
awesome.. thanks alot

are you pulling this info from ur personal knowledge?? or so you know of a website that explains this??

i learned all of this from physics books/classes, so off the top of my head. if you want to know more just say the magic words.

Mr. DudeMan is correct. Very well put I might add.

Air resistance does play a part in Low Earth Orbit (LEO) however.

During the solar storm last week the International Space Station was having difficulties maitaining attitude because the air densiity doubled

<---Works in Mission Control

posted via Palm Life Drive

 

[Ameesh]

the reason is a concept called inertia. essentially it means objects in rest or motion tend to stay that way and the amount of force needed to changed them. the amount of force is related to the mass of the object

 

[silverpig]

Originally posted by: MrDudeMan
first of all, there is most definitely gravity in space. tell your friend that is flat out wrong.

secondly, anything with mass has inertia. inertia is resistance to acceleration. an object with more mass will have more inertia, so while there is less friction in deep space, there is still inertial resistance. you cant say it has no resistance because that includes inertia, making it an untrue statement.

the weight of an object with respect to a given reference frame decreases exponentially as it moves away. when you travel away from the earth, you start to become "lighter" with respect to someone on the surface, but you have to go quite a long distance to start feeling the effects. i calculated it once a year or so ago, but IIRC, you have to be 300+ miles away to be 1% lighter.

something else you may find interesting...there is roughly 1 atom per cubic meter in deep space. this means there is essentially zero particle resistance on the exterior of a spaceship. as i said before, the fact that it cant turn instantaneously is almost purely a function of inertia. rotating a large mass around a point in space is no different than doing it on earth if you do it slowly. why is it hard to push a roundabout on a playground even at slow speeds? air resistance is negligible. if more people get on and sit near the outside of the ring it is even harder. ignoring the resistance of the bearings/bushings holding the platform up, it will become harder to push because there is more mass further away from the center of mass, adding inertial resistance.

another thing to help you visualize...if all of the mountains on earth collapsed to sea level, the earth would spin faster. mountains pull the center of mass of the earth away from the geometric center, and all mass not in the center adds inertial resistance.

Close, but not quite. He's playing star trek. To a good approximation there is no gravity out where starships would be.

And the decrease isn't exponential. It's 1/r^2.

 

[MrDudeMan]

Originally posted by: silverpig

Originally posted by: MrDudeMan
first of all, there is most definitely gravity in space. tell your friend that is flat out wrong.

secondly, anything with mass has inertia. inertia is resistance to acceleration. an object with more mass will have more inertia, so while there is less friction in deep space, there is still inertial resistance. you cant say it has no resistance because that includes inertia, making it an untrue statement.

the weight of an object with respect to a given reference frame decreases exponentially as it moves away. when you travel away from the earth, you start to become "lighter" with respect to someone on the surface, but you have to go quite a long distance to start feeling the effects. i calculated it once a year or so ago, but IIRC, you have to be 300+ miles away to be 1% lighter.

something else you may find interesting...there is roughly 1 atom per cubic meter in deep space. this means there is essentially zero particle resistance on the exterior of a spaceship. as i said before, the fact that it cant turn instantaneously is almost purely a function of inertia. rotating a large mass around a point in space is no different than doing it on earth if you do it slowly. why is it hard to push a roundabout on a playground even at slow speeds? air resistance is negligible. if more people get on and sit near the outside of the ring it is even harder. ignoring the resistance of the bearings/bushings holding the platform up, it will become harder to push because there is more mass further away from the center of mass, adding inertial resistance.

another thing to help you visualize...if all of the mountains on earth collapsed to sea level, the earth would spin faster. mountains pull the center of mass of the earth away from the geometric center, and all mass not in the center adds inertial resistance.

Close, but not quite. He's playing star trek. To a good approximation there is no gravity out where starships would be.

And the decrease isn't exponential. It's 1/r^2.

thats what i meant (the r^2)...sorry, i said it wrong.

 

[OS]

Originally posted by: Gdepp519
ahh. so then.. mass is the only constant.. your weight is relative to where you are??

i think that sounds right.. lol

yeah weight is basically the downward force the mass exerts, and it depends on the strength of gravity.

It just happens since we live on earth, weight/mass is normalized to earth surface gravity. Damn humans thinking we're the center of the universe.