Questions tagged [stability]

Stability theory addresses the stability of potentials, solutions of differential equations, and of trajectories of dynamical systems under small perturbations of initial conditions.

Filter by
Sorted by
Tagged with
0
votes
0answers
86 views

Stability of solar system

As far as I understand, the stability of the Solar system means that planets do not collide and will not in near future. The only thing that is stated on Wikipedia is that scientists are concerned ...
0
votes
1answer
455 views

Stability analysis: small perturbations vs second derivative test

In a mechanical system with some equilibrium point $r_0$, one can do an analysis in order to check if such point is stable or unstable, i.e. the motion of a particle around of it is bounded or ...
0
votes
2answers
112 views

Is physics qualitatively stable if we let Planck's constant tend to zero?

I realise that we can't meaningfully answer the quesition "what is Planck's constant were zero" because it would break out physical models beyond recognition. However, if we let Planck's constant ...
1
vote
0answers
233 views

Pendulum with friction: La Sall's Invariance Theorem

I am trying to understand la Sall's Invariance Theorem, which is used to proove that a system is aysmptotically stable. Can someone help me to understand it, by making an example of how to use it. ...
0
votes
1answer
49 views

Sinking of Cage with weights on one side

If there is a cage with weights strapped on one side, will it always sink towards the weighted side face down? Will the cage rotate so the center of mass is facing downward?
1
vote
2answers
2k views

About the Stability of hydrogen Isotopes

Shouldn't tritium be more stable than a hydrogen atom with no neutrons? Why does tritium do alpha decay but not hydrogen atom with no neutrons? I suppose that when the number of neutrons increases the ...
4
votes
4answers
1k views

Why is it so much easier to fall when walking down a slope?

When I walk uphill on an icey road, I almost never slip/fall. But if I walk downhill or even on a relatively flat road, I slip/fall frequently. What is the physics reason behind this, and are there ...
8
votes
0answers
200 views

Nonlinear stability question

I am looking for a simple example where a system is linearly unstable, but nonlinearly unstable or stable, depending on the sign of the initial perturbation. For instance, assume the linear normal ...
0
votes
1answer
148 views

Decay of hydrogen nucleus?

Very naive question. Nuclear decay is associated to more complex nuclei and explained through radiation. What about hydrogen and less complex nuclei? Will these nuclei eventually break apart? Or is it ...
1
vote
1answer
45 views

Stability of potassium (fermipressure)

I have an exercise to calculate the pressure of the fermigas inside a potassium (bcc, $a = 0.525 \,$nm) crystal. The formula is given with: $p_0 = \frac{2}{5} \, \frac{N}{V} \, E_f(0)$ The result ...
1
vote
0answers
50 views

Is a Niven ring in the atmosphere of Uranus stable? [closed]

For my science fiction universe, I need to mine a lot of Deuterium and Helium-3. I have 10,000 intake fans each capable of 3,000 gigaliters an hour pushing atmosphere through 5 billion diffusers. ...
0
votes
3answers
178 views

Questioning Stability

Today in class my professor was teaching about Einstein's coefficients and in the talk of excited states in spontaneous emission, he was explaining about meta stability of an atom. This made me ...
3
votes
3answers
1k views

Why are the Lagrangian points $L_1$, $L_2$ & $L_3$ unstable?

Why are the Lagrangian points $L_1$, $L_2$ & $L_3$ unstable? I am doing a physics presentation in front of my class and I am just confirming this is correct, and if it isn't, could somebody ...
2
votes
0answers
62 views

Plausibility of a Dyson sphere [duplicate]

So Dyson spheres are generally considered implausible for two main reasons. One, it would an incredible amount (and type) of resources to build one. And two, a Dyson sphere would be unstable because ...
4
votes
1answer
113 views

Moon's orbital plane inclination causes Moon to fall

I read somewhere that if Moon's orbital plane would be perpendicular to the Earth's orbital plane - Moon will fall on Earth within 4 years (given today's position) Can this be shown analytically ...
-2
votes
1answer
352 views

When would Earth's Moon's gravity take over? [closed]

At which point would an object stop being pulled from Earth and towards the moon? Could a light weight rope be tethered to the moon with the object over on Earth's gravity's side? Can it be done and ...
1
vote
1answer
168 views

Righting moment for object submerged in water

I am looking to determine the lateral angle at which an underwater camera system will no longer right itself. When on the ocean floor it is $-24.30~\text{kg}$ buoyant with the difference between its ...
0
votes
2answers
173 views

Stability on a bus

I ride the bus from home to school and vice versa approximately 3-4 times per week for an hour each time. The bus is either bi- or tri-articulated, and it can accelerate to speeds up to 80km/h. Most ...
9
votes
2answers
4k views

Why do modern bicycles have curved front wheel forks?

I can't help but wonder how the design might affect the stability of the the bicycle. How would it make a difference if they were straight, or curved much more than they usually are?
3
votes
2answers
2k views

Why do rope walkers always carry a long stick with them?

I saw in the film (based on a true story) "The walk" a guy who tried (and succeeded) to go from one high building to another via a rope. He even succeeded in going from one the (then still existing) ...
1
vote
1answer
329 views

How to determine the overturning moment on a stand alone, uncovered bean pole tipi [closed]

I will preface this by saying I am a highschool student who has not yet had a physics class. I engineered and built a hexagonal shaped, open bottomed, planter to hold soil that would contain pole ...
0
votes
0answers
64 views

Would it be correct to state that all the forms of everyday matter (mountains, tables, buildings, people, etc.) are in a metastable state?

We had a fire going in the backyard of a friends house this weekend, and after thinking about the chemical reactions occurring in the wood (and anything else we threw into the pit), I started to ...
0
votes
2answers
89 views

Question about a Attractors in Non-linear Systems

I've recently been reading up on non-linear dynamics and came across the concept of attractors. I'd like to ask if the concept of attractors can be used for pedestrian egress from a room? Since ...
13
votes
7answers
2k views

Why doesn't an object, despite having a non-zero potential energy stored in it, fall by itself from the elevation?

When an object is at a certain height, it has some energy stored in it as we have done some work on it to get it to that height. So when it already has energy, then why doesn't it fall off from the ...
0
votes
0answers
222 views

Stabilizing a shaft with only one electromagnet

I have recently come across Earnshaw's theorem in my research which states that it is not possible to stabilize an object using only static permanent magnets. I understand that and it makes sense to ...
2
votes
0answers
1k views

Why are symmetrical structures highly stable? [closed]

What makes symmetrical structures(geometry) highly stable? It is perfect to say that the forces acting on a symmetrical structure is balanced and hence stable. But why is it so? To be more specific, ...
1
vote
2answers
606 views

Why can't we put an object anywhere in the earth's orbit around the sun instead of Lagrangian points?

If we place an object in the earth's orbit around the sun, it should have the same orbital period right? For example, what would be the behavior of an object in orbit at point A1? It is at the same ...
7
votes
1answer
588 views

Lyapunov stability of circular orbits

I'm studying Classical mechanics on Arnold's "Mathematical Methods of Classical Mechanics". In a problem I am asked to find for which $\alpha$ the circular orbits in the central field problem are ...
1
vote
0answers
109 views

Imaginary part of the stress-energy tensor

I just encountered in an article of D. G. Boulware ("Quantum Field Theory in Schwarzschild and Rindler Spaces", Phys. Rev. D 11, 1404, 1975, in the last paragraph of the Introduction) the statement ...
3
votes
3answers
160 views

Could the Earth-Moon rotation period equal one Earth year?

I just stumbled on this rather confused QA. The point seems to be if the Earth-Moon rotation period was identical to the Earth-year, then ... ... all three would stay in a line at all times. Could ...
0
votes
1answer
379 views

conditions for something being being considered as a system? [closed]

without loss of generality can somebody answer the question in reference to a car being towed by a truck. I am asking this question because the work done by the truck on the car is different at ...
2
votes
1answer
19k views

Calculating the tipping point of a lamp post

So I'm designing an outdoor lamp post and trying to calculate whether it will withstand the heavy winds at the worst case scenario. Here are the parameters and what I've done so far: The lamp post is ...
39
votes
4answers
17k views

Why do most office chairs have 5 wheels?

(Inspired by Why are four legged chairs so common?) I've been wondering for a while... Why do most wheeled office chairs have 5 wheels? My guess would be that while stability vs. simplicity results ...
4
votes
4answers
576 views

How are orbits made stable?

I understand the concept of object staying in some orbit due to centrifugal force and gravity. However I do not understand how is orbit of a body like satellite or planet has perfect balance between ...
11
votes
2answers
553 views

Is this a correct demonstration for why elements above untriseptium cannot exist?

With the confirmation that elements 113, 115, 117, and 118 are indeed fundamental elements that are now to be named on the periodic table, the next question is: what is the highest atomic number ...
5
votes
1answer
537 views

Doubt in Dyson's argument about the divergent nature of the perturbative expansion in QED

I am trying to understand Dyson's argument about the divergent nature of the perturbative expansion in QED. Quoting his own words [...] let $$F(e^2)=a_0+a_1e^2+a_2e^4+\ldots$$ be a physical ...
2
votes
2answers
874 views

Is there any stable hadron?

Neutron can decay into proton and I think some hypothesis claim that proton can also undergoes decay into subatomic particles... Is there any hadron that never decays?
5
votes
1answer
107 views

Does the maximally-extended Schwarzschild horizon see the entire past of the parallel universe?

I've seen similar discussions for the inner horizons of Kerr and Reissner-Nordstöm metrics, but I've never seen mention for the simple maximally extended Schwarzschild geometry: As an infalling ...
1
vote
2answers
301 views

Why does the mass on the cart-pole have to fall?

Not sure if I am posting this question in the correct community, as it relates primarily to reinforcement learning. Apologies early on if this is not so. In reinforcement learning many algorithms ...
3
votes
1answer
86 views

Can a spheromak propagate in vacuum?

I recently learned about (and am now fascinated by) spheromaks. I am no expert on plasma physics, but as I understand they are analogous to propagating toroidal vortices (smoke rings), but with plasma ...
3
votes
2answers
783 views

What are the Kinematics of an Irregular Tripod?

It is a common maxim (at least within the Scouting community) that a triangle is the most stable shape. In practice this means structures should have three legs whenever possible, and have cross-bars ...
0
votes
1answer
246 views

Is it okay to put singularities into the wave function to test behavior around unstable potentials? [closed]

$$ \psi(r)=\sqrt[4]{\frac{ a}{8\pi^3 }}\frac{ \exp (-a r)}{r^{1.25}} $$ The wave function above is an example of a function that is normalizable in 3D space and $r=\sqrt{x^2+y^2+z^2}$. $$ -\psi ''(r)...
1
vote
1answer
113 views

Can a natural satellite have a synchronous orbit?

I was thinking about space-elevators and large masses being put into geosynchronous orbit, when I considered the possibility of a natural satellite being in a synchronous orbit. I did a little digging ...
0
votes
0answers
33 views

Is it possible that any spatial variation in press disturbance without gravity?

When gravity (and buoyancy), acting as the only body force of a liquid, is ignored. Is it possible that any spatial variations in pressure perturbation are the result of fluid motion or some other ...
34
votes
7answers
3k views

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles?

How can the unstable particles of the standard model be considered particles in their own right if they immediately decay into stable particles? It would appear to a layman such as myself that these ...
2
votes
1answer
809 views

growth rate of the instability of a laminar flow?

I was just studying something about The Plateau-Rayleigh Instability that I saw something called Growth rate of the instability. My question is the exact physical definition of growth rate of ...
3
votes
1answer
69 views

What does the g mean after the isotope given?

I'm familiar with notation such as Sc-44m standing for the meta stable state of Sc-44. What does Sc-44g mean? There are a few examples of this notation; here's one: http://iopscience.iop.org/0031-...
1
vote
1answer
122 views

Can 4 collinear planets exist?

Imagine 4 planets, A has moon a and B has moon b. A and B are binary planets. Is it possible that a and b and A + B all have same the period, so that the 4 planets are collinear?
7
votes
1answer
2k views

How “large” is a Lagrange point?

When placing an object at a L-point, the natural assumption, as with all things gravity, is that you needn't place it in an exact spot to achieve a stable configuration. How much room do you have to ...
1
vote
3answers
5k views

Why don't electrons collide among themselves

The Heisenberg principle states that we cannot ascertain simultaneously the position or momentum of any small particle. However slight, is there a chance that 2 or more electrons from the same or ...

1
4
5
6 7 8