Need help generating gravity

[iglak]

MrL_JaKiri said in post # :

The alpha is a very crude version of the symbol meaning 'proportional to'.

 

Mass is proportional to density.

ah, okay, that makes sense. thx

[JaKiri]

Crash said in post # :

its irrelevant to the story, but you have to manufacture it in the spot you wanted it to remain

 

Why? Why CAN'T we move it?

 

F=ma duder.

[greg1917]

i don't know what that means, can you explain?

 

Mass varies as density.

 

A material with a higher density will have a higher mass than the same volume of a less dense material.

 

Thus density affects gravity and is an important consideration.

[YT2095]

this might be a mad idea as it`s based on a guess. if Earth were to stop rotating (slowly of course) would we weigh more?

obviouly our masses would remain constant, but the velocity we rotate at may have a "lightening" effect due to centripetal force.

maybe stopping Mars` rotation or slowing it could allow it`s natural gravity to have a greater effect?

 

I don`t know the maths or even if it`ll work, it maybe complete bull$h!t, but it`s an idea

[Aliasalpha]

I'd have thought the rotation would increase our weight rather than decrease it.

 

Hmm, I've just come up with a zany scheme to lose weight!

Step 1: Halt earth...

[YT2095]

it would increase weight if you were inside it like in a ball and it was spinning.

 

if you stopped the roation, my guess is that it would do one of 2 things, you`de gain weight, or it would have no effect.

I don`t know enough to comment

[Atlantic]

Mars is quite close to earth gravity, so i wouldn't go that far

[alt_f13]

YT2095 said in post # :

it would increase weight if you were inside it like in a ball and it was spinning.

 

if you stopped the roation, my guess is that it would do one of 2 things, you`de gain weight, or it would have no effect.

I don`t know enough to comment

 

 

 

I did the math once.  You do gain weight but not much.. I'll do it again and edit the post.

 

 

 

[edit]

 

Aight, check it, yo.

 

 

 

Earth's radius = 6.38 * 10^6 m = Re

 

Centripital accelleration at the surface = 4* Pi ^2 * R / T^2 = Ac

 

Accelleration due to gravity at Earth's surface = G * M / R = 6.67 * 10^-11 * 5.98 * 10^24 / (6.38 * 10^6)^2

 

=9.79909

 

Seconds in a day = 24 * 60 ^ 2 = 8.64 * 10^4

 

 

SO...

 

Your weight because of the earth's rotation is:

 

Ag + Ac = Ay * my (Accelleration on you times your mass)

 

9.79909 - 4 * Pi^2 * 6.38 *10^6 / 86400^2 = Ay

 

9.79909 - 0.03374 = Ay

 

9.79909 - 0.03374 = 9.76535

 

 

 

 

So the force on you now is 9.76535 * your mass.

 

The force on you w/o the rotation of the earth is 9.79909 * your mass.

 

The difference is 0.03374 * your mass.

 

 

 

 

To find out what the weight difference is in pounds take 0.03374 * your mass in kg * 0.22481

 

Or if you only know your weight in pounds, take your weight in pounds * 4.4475 / 9.76535 to get your mass and do the line above.

 

 

 

 

(Yah, I know there is an easier way to do it in pounds w/o all the newton stuff but imperial is for dorks and I didn't want to do any more math.)

[Crash]

well MrL_JaKiri

if were talkin superdense matter here, superdense enough to considerably raise the gravity of mars then

F=(insert large # here)*acceleration, i take it then that 'F' stands for F**]<in heaps

[Aliasalpha]

Actually that's an interesting point for my story, If I have say 20 chunks of superdense matter with cities perched on top would that be enough to alter the rotation or orbit of mars? I didn't plan to have them at even intervals or anything, just on the nice flat areas so would that create an imbalance?

[YT2095]

I would esstimate that a mass large enough to create a "normal" Earth gravity under a city(s) wouls also make a "wobble" as the rotation would be eccentric as a result.

in effect, it would be a BAD idea even if it were possible.

[Pinch Paxton]

Your book is getting too detailed in my oppinion. I'm a writer too!

[JaKiri]

Crash said in post # :

well MrL_JaKiri

if were talkin superdense matter here, superdense enough to considerably raise the gravity of mars then

F=(insert large # here)*acceleration, i take it then that 'F' stands for F**]<in heaps

 

No, a force of 1N would do it. Might take a long time, but it'd do it.

[JaKiri]

alt_f13 said in post # :

Your weight because of the earth's rotation is:

 

I don't see quite where this is going, or what it's meant to demonstrate.

[alt_f13]

YT2095 said in post # :

this might be a mad idea as it`s based on a guess. if Earth were to stop rotating (slowly of course) would we weigh more?

obviouly our masses would remain constant, but the velocity we rotate at may have a "lightening" effect due to centripetal force.

maybe stopping Mars` rotation or slowing it could allow it`s natural gravity to have a greater effect?

 

I don`t know the maths or even if it`ll work, it maybe complete bull$h!t, but it`s an idea

 

 

 

The point is I would weigh half a pound more if the Earth was not rotating.  That is the effect of centripital force on a person on the surface of the Earth.  Almost negligable. 

 

 

 

Seeing as Mars is smaller it would have more of an effect but certanly not 50%.

[Aliasalpha]

Pinch Paxton said in post # :

Your book is getting too detailed in my oppinion. I'm a writer too!

 

Oh I wasn't planning on using that in the story, it was just a though

[ski_power]

One question about gravity. In a ring planet(a la Halo), will it be possible for natural gravity to occur. And assuming that it's characteristics(ie mass, density, angular momentum etc) are identical to the earth, then how much g would it exert on us?

 

PS: Are you guys geniuses or what?

[YT2095]

by "in a ring planet" do you mean a normal planet with rings? like Saturn or Uranus?

I think such a planet would have an additional "tidal" effect, but be so tiny as to be hardly measurable without equpment, but certainly a ring around a planet would have a gravitational effect much in the same way as our moon does, but it would be less pronounced as the moon`s a single dense object and moves quite quickly, whereas a ring is almost a constant mass in average density (assuming no moons).

 

secondly, I personaly do not consider myself a Genius. I`m just a ME

[ski_power]

When I said ring planet, I actually meant a planet which is in the form of a ring. And it spins along it's diameter.

[Sayonara]

Certainly a Halo would have a gravitational pull, assuming of course it has mass which the thing you're talking about invariably would.

 

How close it was to Earth's gravitational pull would depend on the ring's dimensions and density.

 

I'm not sure how to work it out exactly but it would probably have to be one fat (or deep) ring.

[YT2095]

When I said ring planet, I actually meant a planet which is in the form of a ring. And it spins along it's diameter.

 

I`ve never heard of such a beast in all honesty (not to say it couldn`t exist however if made of strong enough material)

speeding up the rotation of such a structure would indeed inrease the centripetal force and weight of the folks inside the diameter of this ring of course.

I do however fail to see HOW this effect may apply to Mars that has no such facility?

[Sayonara]

I`ve never heard of such a beast in all honesty

It's like a Dyson Sphere, only it's a ribbon instead of a shell. Slightly more feasible

[swansont]

Certainly a Halo would have a gravitational pull' date=' assuming of course it has mass which the thing you're talking about invariably would.

 

How close it was to Earth's gravitational pull would depend on the ring's dimensions and density.

 

I'm not sure how to work it out exactly but it would probably have to be one fat (or deep) ring.[/quote']

 

There would be no gravity on the inside of the ring. Assuming a uniform mass distribution, gravity depends on the mass inside of your radius. This is from Gauss's law (used also in electrostatics - if the ring were charged there would be no electric field inside, either)

 

Whatever pull there is from the mass below your feet, it is counterbalanced by all the mass elsewhere in the ring. The sideways pull cancels from symmetry, but the up/down cancels, too. Even though a lot of the ring is far away, there's a lot of it compared to what's below you.

[ski_power]

But wouldn't Centripetal Acceleration give us gravity on the inside part of the ring?

[ski_power]

But wouldn't Centripetal Acceleration give us gravity on the inside part of the ring? Assuming it is rotating along it's principal axis, ie perpendicular to the plane through the centre