A Question?

[rajeshrathee]

1. The Centre of gravity of a vessel is dependent on its ingradients, like a vessel having a solid will have a centre of gravity at a different place then a a vessel having hay. If we took out a bit of ingradients out of the vessel then again its Gravity centre changes. It changes even if we take out the ingradient from inside it and keep it on its top.

Now as we are taking out metals etc out of earth regualrly then are we increasing a chance of disturbing its Centre of gravity and if yes then what can b the consequences.

Doosra sawal is sawal ke jawab ke bad....... ;)

[vikasbaliyan]

1. The Centre of gravity of a vessel is dependent on its ingradients, like a vessel having a solid will have a centre of gravity at a different place then a a vessel having hay. If we took out a bit of ingradients out of the vessel then again its Gravity centre changes. It changes even if we take out the ingradient from inside it and keep it on its top.

Now as we are taking out metals etc out of earth regualrly then are we increasing a chance of disturbing its Centre of gravity and if yes then what can b the consequences.

Doosra sawal is sawal ke jawab ke bad....... ;)Dear Rajesh Bhai You are very much correct but is it possible to take out all the metals out of earth. I feel it is impossible and the centre of gravity will be same.

VIKAS

[uday]

Rathee sahab,
Ram.. Ram.
Bol ko haath se kitneyhi upper faink lo..padeygi dhartee per hi aa kar :p
If we fire som metal out of orbit which will never come back to earth gravity ..is insignificant in concern to earth's gravity.

[srajdeep]

1. The Centre of gravity of a vessel is dependent on its ingradients, like a vessel having a solid will have a centre of gravity at a different place then a a vessel having hay. If we took out a bit of ingradients out of the vessel then again its Gravity centre changes. It changes even if we take out the ingradient from inside it and keep it on its top.

Now as we are taking out metals etc out of earth regualrly then are we increasing a chance of disturbing its Centre of gravity and if yes then what can b the consequences.

Doosra sawal is sawal ke jawab ke bad....... ;)

Hi Rajesh
The question is valid. Only thing you forgot was that earth is a layered sphere. Top most part is the earth which is around 60km deep and so far the deepest mine is around 15km deep (somewhere in South Africa). Earth's radius is 6000Km. so in a way all the metals we are taking out is from only 1% of earth's depth. Now all the mines on eath might only occupy less than 0.001% of earth's surface. (remember more than 70% of earth's surface is just water adn rest had things like sahara/antartica/arctic)
Another thing due to centrefugal the earth's crust has the lightest elements (the more heavy stuff is still deep inside the core) Most of earth's weight lies deep inside in "inner core". So using you analogy is is like saying that you have a metal pot which is very thick and is filled with (let's say) sand. now you are just taking out .0001% of top 1% layer of this sand and displacing it by 1% depth. So your center of gravity will change but not more than few nano meters. If we think in earth's scale you are changing the CG to only few micrometers which won't make any difference.
hope it helps

raju

[rajeshrathee]

thanx all
this question comes 2 my mind when i was in 5th class but i asked this onlynthis time
rajesh

[bharatrattan]

thanx all
this question comes 2 my mind when i was in 5th class but i asked this onlynthis time
rajesh

I think all of you have missed the right explanation.
Physics is something I cherished and read in detail about seven years back.
The extent of theoritcal phyisics I read during my +2 offers a very simple answer. But I dont know how convinced you will be (since it is an axiom/Law).

Since the earth and people living on it form a closed internal system (closed internal system is something like mass m1, m2, m3 .....with no external force acting on it) , interaction between its elements ie man (one element) excavating the earth (other element) for mining etc. can not change its centre of Gravity. (not even by one indefinitly small point, absolutely zero change)
This is one of the central laws of newtonian/classical phyisics, which can directly be derived from Newton's Laws of Physics.
One of the interesting ways to put is that "a rider riding a horse, can not slow the horse by pulling his hairs backword."
I think smarties can proove mathematically what I have said.
Bharat

[devendramalik]

My Thoughts:

It is simple - the matter can neither be created, nor destroyed...
It will always remain on earth (which is close to being a sphere) until the atmospheric blanket is wiped off... Hence CG will remain almost intact....
But mind it, a huge collision from a comet or meteorite (at least of the size of a football field) can alter the direction of rotation of the earth... Scientists are also exploring the result of recent Tsunami which has changed the polar tilt of the earth, though minutely....



The amount of metal extraction we do from earth every year is approx 0.001012% from the total mass of the earth.(Courtesy: NGC planet)Also the amount of extraction done is compensated by the birth rate of various species and the amount of debris which goes into the earth every day.

Even if you say the shift in CG may drift the planet orbital path away then the reply would be elliptical orbit of any planet around the sun has helical attraction force just like Electrons inside the atom which compensates for the loss of orbit.Any nuclear explosion tends to increase the diameterically distance between the fathest points of the elliptical path thereby experiencing a hot long summer day or cold long winter night at times

So the CG is not shifted much.For a planet of the size of earth with a diameter of 86400KMs, i guess microns of change in CG will hardly effect anything

[vinodks]

Well, both Rajdeep and Bharat are right and both are wrong too :-)
1) If you consider change of CG of earth w.r.t. "external objects" like sun, moon etc then no amount of distortion of earth's shape by "internal agencies" like human can change its CG... center of globe(not CG) will move in such a way as to bring new CG exactly at the same position w.r.t. external objects... also this will not change momentum of earth(horse-rider analogy of Bharat explains that).... however, collision of comets will change both momentum and CG....

2) But if we imagine displacement of CG of earth w.r.t. physical center of earth(if taken as solid sphere which is not completely true), it will definitely change with excavation of material from earth but ONLY IF this excavation is non-uniform through-out earth's surface... if you keep piling lots of material at one place you are literally pushing earth down w.r.t. stars but CG is at same place w.r.t. stars BUT CG is moving away from center of earth... but here we MUST talk in terms of degrees(Rajdeep gave nice figures) and with current amount of dispalcement of material this kind of change can be neglected..... One more important point... with displaced CG of earth all objects on earth's surface WILL NOT feel gravitaional force towards earth's center but little away from it that might induce automatic displacement of material to minimise energy e.g. sea level will certainly not be spherical which it is right now(if we neglect moon's gravitation and earth's rotation), tall buildings might fall(which anyway are not made perpendicular to earth's surface right now inorder to compensate earth's attraction and centrifugal force depending on how far building is from equator).. (this automatic change of shape will try to restore original position of earth's CG) and all of it will be hodge podge.... but right now this effect is very very very small.... I will leave exact calculation of numbers to more enlightened souls :-)


Vinod