orbit question (1 Viewer)

[Ragerunner]

What maintains a space station in orbit around the earth ?

i know gravitation field is one but what is the other ?

i was thinking centripetal force ?

 

[...]

centripal force??? hmm...i dunno if thats true...coz from my teacher, he taught me that if an object has a force acted upon it, there must be something touching it....this does not applied to Gravitation force, Magnetic force or Electromagnetic...(i think thats the 3)

and from the satellite orbiting...only gravitation force is possible...

this could be very wrong, so someone correct me quickly

 

[kini mini]

Originally posted by Ragerunner
What maintains a space station in orbit around the earth ?

A space station is assembled in space from components that were given some orbital velocity when they were launched, the interaction between this kinetic energy the station has and the gravitational field of the Earth determines its orbit. The gravitational force IS the centripetal force.

Originally posted by ...

he taught me that if an object has a force acted upon it, there must be something touching it....this does not applied to Gravitation force, Magnetic force or Electromagnetic...(i think thats the 3)

You don't have to worry about the way forces work, you can just use the Newtonian concept of "action at a distance". I believe the current model for gravity for instance is the exchange of the graviton.

 

[Constip8edSkunk]

there are also constant adjustments made by the spacestation itself i think so that it doesnt slowly spiral down towards earth as there are always some energy lost...

 

[Ragerunner]

teacher said its gravity and something about horizontal motion

i put my answer as gravity and centripetal force

 

[Ragerunner]

would centripetal force get a mark as an answer ?

 

[Lazarus]

Originally posted by Ragerunner
would centripetal force get a mark as an answer ?

That would depend on the exact wording of the question, and the number of marks available. I'll assume it to be as you originally said, asking what "maintains a space station in orbit".

In my mind, there are two possible correct answers (and also equivalent variants of them).

One would describe an equilibrium relationship between the centripetal force (due to gravity) and the space station's tangential velocity. Both of these components are necessary for the space station to remain in orbit. If you had only the former, it would spiral into the planet, and if you had only the latter, it would fly out into space.

The other explanation is similar but doesn't specifically refer to the forces. The space station is, in effect, continously falling towards the planet, but due to the fact that the station is moving perpendicularly to the line between the station and the planet, the surface of the planet curves away from the falling station at the same rate at which it falls.

The emphasis should really be on the equilibrium relationship, and not the nature of the forces themselves; were I the marker, I would have awarded half a mark for each force you mentioned (or indirectly described) and one mark for a description of the relationship between them.

 

[Ragerunner]

basically the 2 answers in our exam to get both marks for it were "gravity" and "horizontal something" can't remmeber

i was awarded one mark for gravity and i thought i read in a book about the earth and a satellite in orbit maintains its orbit much like the tension in a string of a whirling rock.

so i said centripetal force. apparently its TOTALLY wrong he said

i told him i thought i remembered i saw it said something like that in a textbook.

he replied hastily with "Bullshit" ( in those exact words )

 

[Lazarus]

Mmm, well, he may be right. I vaguely remember my physics teacher explaining once that there's actually no such thing as a centripetal force and we should only refer to gravity or something.

But I've forgotten the specifics, sorry.

[Edit - ...'s version sounds good.]

 

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as far as i can remember, u can only put centripal force if something is touching it...as i said earlier...and i think that as a weight swings around, the string from the weight is pulling the weights towards the centre, the string carries a centripal force on the weight(now is that how u state it?)

 

[+:: $i[Q]u3 ::+]

cyph is right about centripetal.. except dude... acceleration isnt a component of a force... it isn't a force... sorri...

ragerunner. the answer to your question
"what maintains a space station in orbit"
is the gravitational attraction between it and the earth.
this is the gravitational force.
the only force.

the 'centripetal force' is just a name we give to a particular force that acts to make something spin; and it's directed towards the centre. In this case, the gravitational force IS the centripetal force; it acts towards the centre of orbit (earth). (yup.. try equating the eqation for centripetal force: F = mv^2/r with gravitaional force: F = Gm1m2/r^2 and you'll get the orbital velocity for a satellite... ^^)

everyone reckons its weird that there's only one force... but that's what scientists say, and it's to do with the derivation of the force equation.. engineers do it a different way and they end up with another 'force' (wel.. a pseudoforce...) outwards.. but we aint engineers ^.^

erm. yes. i'm a physics nerd. *-.-;;; haha.. wat can u do..
hehe.. anyway, hope that helps

 

[+:: $i[Q]u3 ::+]

sorry cyph.. i'll clarify as well.. ^.^

the grav. attraction is the only force btwn earth n the satellite.
the acceleration of the satellite is in the same direction as the force... that is, the satellite is accelerating towards the earth.

 

[Lazarus]

Originally posted by Lazarus
Mmm, well, he may be right. I vaguely remember my physics teacher explaining once that there's actually no such thing as a centripetal force and we should only refer to gravity or something.

Hah! I remembered why last night!

There's no need for a 'centripetal force', and indeed such a force does not exist. With a satellite orbiting a planet, the relevant force is gravity. With an object being spun on a piece of string, the relevant force is the tension of the string. In both cases, if the force is exceeded, the projectile will be flung outwards.

I feel much better now.

 

[...]

Originally posted by Lazarus
There's no need for a 'centripetal force', and indeed such a force does not exist. With a satellite orbiting a planet, the relevant force is gravity. With an object being spun on a piece of string, the relevant force is the tension of the string. In both cases, if the force is exceeded, the projectile will be flung outwards.

that was wat i was putting across in my first msg

 

[Ragerunner]

2 forces are gravity and horizontal velocity required to maintain it.

the centripetal force is the result of those 2

thats why i got the quesiton wrong

 

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horizontal velocity is not a force....

 

[Constip8edSkunk]

uhh... i thought gravity is the centripetal force involved in this case...

 

[kini mini]

Horizontal velocity is not a force. Velocity in general is not a force. The only force here is the force of gravity.

 

[Ragerunner]

well our teacher asked for 2 forces that kept a space station in orbit around earth.

whether its right or wrong i won't get the mark anyway

 

[+:: $i[Q]u3 ::+]

Originally posted by Ragerunner
well our teacher asked for 2 forces that kept a space station in orbit around earth.

whether its right or wrong i won't get the mark anyway

wat the hell?

the only force is the gravitational (ie. centripetal) force.
it's kept in orbit by its velocity, but velocity is NOT a force~!!!

bloody incompetent teachers... -.-;;
sorry... don't worry... my teachers are like that as well....
lol....

mano man... oh hang on thought of something quite funni.. i'll post another thread actually...

(btw sorri for insulting ur teachers ragerunner.. i don't mean anything personal... really.... >.<)