Questions tagged [orbital-motion]
The path a body takes while moving through space under the influence of the gravitational forces of other bodies
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Horseshoe orbit cycle times
I asked on Worldbuilding originally, but was directed here instead
I've been working on a habitable moon system for a story, and I'm now trying to populate the other moons around the parent planet. ...
3
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2answers
118 views
Circular orbit in a central force field
Considering a motion of a body under a attractive central force,
$\textbf{F}(\textbf{r}) = -\frac{k}{r^3} \hspace{1mm}\hat{\textbf{r}}$ with $k>0$.
Is it possible for a body to move in an at ...
3
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2answers
86 views
Is a stable orbit possible inside the ergosphere of a Kerr (spinning) black hole?
I have heard that it's "impossible to hover" inside of an ergosphere, but everywhere I read this seemed to be speaking in the context of "relative to a stationary observer outside of the ergosphere". ...
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3answers
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Why does angular momentum being constant prove Kepler's first law?
So I was watching this video and this video on Kepler's first law in order to understand the proof of Kepler's first law. He started off by saying that for an ellipse, the distance from a focus point ...
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Thought experiment. Earth orbital motion if we stopped Earth spinning
This is a thought experiment that puzzles me. Imagine we could magically stop Earth’s rotation around its own axis (and locally verify it by disappearance of inertial forces generated by the spin ...
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1answer
43 views
How fast would an object at cruising altitude (around 10,600 m) need to travel to stay on the opposite side of the Earth to the Moon? [closed]
I am trying to figure out how fast an object will have to travel (at a height around 10,600 m) to never be in the presence of the moon. Meaning the object will always be on the opposite side of the ...
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1answer
31 views
I have a question about the gravity probe B geodectic precession formula and why it seems to be twice the planetary precession formula
Specifically, I can work out the planetary precession formula to give radians per orbit as
6*pi*GM/c^2r
(and I find that on the web at places like http://farside.ph.utexas.edu/teaching/336k/...
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Force of gravity [duplicate]
I want to know why isn't the moon fall on earth instead of floating on top or going around the earth without even falling on earth by the force of gravity on earth .
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What determines the direction of an object that has undergone the effect of a gravitational slingshot?
I just started researching this topic and therefore I do not know much about it. Nonetheless, I am still curious about what determines the direction an object takes after passing by a planet. I think ...
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Constraints on the mass distribution within each body such that their mutual orbits are Keplerian?
The trajectories of two point masses with respect to their center of mass are conic sections or Kepler orbits.
But what if the bodies have finite size with respect to their separation, and not ...
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1answer
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On Planets orbiting binary stars
Several years ago a discovery was made of planet orbiting a star of a binary system (two stars orbiting each other). Since binary star systems are plentiful in our galaxy, I presume we will be ...
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If gravitation force varied with $r^{-3}$ instead of $r^{-2}$ what would happen to Kepler's laws [duplicate]
2nd law wouldn't change as it is LCAM. 3rd Law would change. But I'm confused about first law. Does any body under influence of any central force move in an ellipse?Can anyone give a simple proof/...
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1answer
41 views
How does the Earth's radial acceleration affect it's velocity during orbit around Sun? [closed]
When the earth moves along its ellipse at $67,000mph $ it accelerates at $0.006m/s^2$ would it be correct to say it's speed at some points relatively increases by $0.006m/s$ every second
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2answers
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Which force described the “absolute” speed change of the moon in Newtonian mechanics?
In the world of "absolute" speed values in the Newtonian mechanics, the moon must move faster (i.e., must have a higher speed) if he travels with the earth (i.e., has the same velocity direction) than ...
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1answer
39 views
What's the Earth's linear acceleration component around the Sun?
The earth's centripetal acceleration around the Sun is $0.006m/s^2$ does this mean one can say the earth's acceleration when it travels(revolves) at $670,000mph$ is simply equal to its centripetal ...
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2answers
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Shouldn't ball has to move in the circle even after cutting the rope by which it was attached? [closed]
Since the tension force is a central acting force, the torque on an orbiting ball about that center is zero. But if the rope is cut down during motion the torque would still remain zero. This would ...
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1answer
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Centrifugal force in effective potential
$$E = \frac { 1 } { 2 } m v _ { r } ^ { 2 } + \frac { L ^ { 2 } } { 2 m r ^ { 2 } } + U ( r )$$
This is the formula of total energy of an object with mass $m$ orbiting an assumed stationary body of ...
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2answers
163 views
I'm travelling near the speed of light. Do I need to brake before using a super-massive black hole to turn around?
I'm taking one of those new fusion drives for a trip to nearby supermassive black hole. At a comfortable 1 G, it'll take me about 7 months of proper time to accelerate to 95% the speed of light. I'm ...
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1answer
36 views
What is Earth's current true anomaly from j2000?
I enjoy amateur astronomical calculations. I calculate earth true anomaly and noticed a bug in my software just as earth passing through j2000 point and instead of going to 0 degrees it subtracting ...
2
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1answer
77 views
'Harmony of the Spheres' or 'Harmony of the World' - is it debunked? [closed]
I sincerely apologise for this vague question but I'm writing an essay for my music class on musical harmony and it's historical origins. I came across the Pythagorean notion of Harmony of the Spheres ...
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Is the total mechanical energy of a satellite constant, regardless of its orbital radius?
If a satellite moves outwards into an orbit that is at a greater distance from the centre of Earth, work has been done. As work is the sum of the change in kinetic energy and gravitational PE, has the ...
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3answers
121 views
If a satellite moves towards Earth, is negative work done against the force of gravity?
A bit confused here - if a satellite approaches Earth, its displacement is in the same direction as the gravitational force (towards the centre of rotation). Therefore, gravity is doing positive work?
...
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Is the derived equation for the lift coefficient showed below for an airplane in orbit right?
For an airplane flying in an orbit around the Earth the gravitational force minus the lift force would equal the force caused by the acceleration towards the centre of the Earth.
$$ \frac{GM_Em}{(R+h)...
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1answer
48 views
Lagrangian Equation of Motion for Planetary Orbit in a Single Plane
Assume that a mass $m$ is in a gravitational orbit around a much larger mass $M$, as in the case of the earth revolving around the sun. Also, assume the motion is constrained to a single horizontal $...
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Show me how the sky is like in Jupiter (but not mars)
Assuming someone is "standing" on the "surface" of Jupiter (ok, in a stable position deep inside the gas giant's gravity field analog to standing on the surface of a rock planet) where the moons can ...
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2answers
62 views
Is the period a physical observable in General Relativity?
I am currently seeing the classical tests of GR. To justify the introduction of a test based on the Doppler effect, the professor says that the previous test ( Shapiro and echo-radar test ) is based ...
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1answer
58 views
What is the second $r$ in this equation for the Two Body Problem?
$$r=\frac{r^2\frac{\mathrm d\theta^2}{\mathrm dt}}{\frac{Gm_2^3}{\left(m_1+m_2\right)^2}\left(1+e\cos\theta\right)}$$
I have this equation for the radial distance of a planet from the barycenter. But ...
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1answer
46 views
Bad value for sphere of influence with Venus [closed]
I would like to get value of sphere of influence than Wikipedia for Venus:
on https://en.wikipedia.org/wiki/Sphere_of_influence_%28astrodynamics%29
It is indicated for Venus: $S_{\text{OI}}=0.616\,\...
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1answer
79 views
How do compute an energy momentum tensor, given some equations of motion
This problem can be found in a paper called "Gravitational Radiation From Point Masses In A Keplerian Orbit", but I do not have access to this, so cannot see how to do it.
I have been given a ...
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1answer
62 views
Motion of the center of mass of rigid bodies in space
For the classic two body problem, I know that the motion of the center of mass is a straight line (with respect to an inertial frame), provided that the bodies are considered as point particles.
Now ...
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Are galaxies rotating faster or slower over time?
Independent of the discussion around flat rotation curves and dark matter, is there something known about the change of the rotation curves over time?
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3answers
603 views
Sci-fi ships falling on planets
I hope the question is suitable for this forum....
Watching Star Trek: The Next Generation, I have found at least a couple cases where a navigation malfunction on a shuttle makes it fall towards the ...
2
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2answers
63 views
Periods of non-circular Schwarzschild orbits
I have been thinking about non-circular orbits in the Schwarzschild spacetime. How would you define a period of one orbit? I was thinking, in terms of proper time, for $r$, how long it takes to go ...
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5answers
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What is holding things like the Earth and the Sun in one dimension?
I was thinking last night: for most of my life I’ve been taught that the planets in our solar system orbit the Sun, which insinuates that the Sun is in a fixed point in 3-dimensional space, and that ...
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Examples of central forces on the path of orbit?
In solving a problem from Goldstein (3.13), I solved for multiple properties of a circular orbit with the attractive central force where the path of orbit crosses the point of the force (at origin).
...
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1answer
48 views
Is the Earth orbiting an 'illusory' Sun, owing to the 'speed' of gravity? [duplicate]
We see the Sun about eight minutes after light left it. Presumably this means we are also experiencing the Sun's gravity 8 minutes after it 'left' the Sun.
So are we orbiting around the Sun we can ...
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1answer
24 views
Barycenter of a binary star system
It is said that the barycenter of 11 Draconis (Thuban) and 10 Draconis which compose a binary star system is a central point. Is this central point a material or immaterial object? Does the size of ...
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1answer
58 views
Why do the orbit equations have to be symmetric about two axes even the orbit is not bounded?
In the book of Classical Mechanics by Goldstein, at page 88, it is given that
However, the orbit might not be bounded, so there might not be two turning point; just one. In such a case, how can we ...
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2answers
90 views
Why aren't shape of galaxies depicted as a funnel?
Let's say if a galaxy is moving, shouldn't it be shaped like a funnel? I am saying this because it would take considerable time for the outermost star to know that the center of gravity has shifted. ...
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1answer
25 views
How is Geo Stationary Rocket placed exactly above the Location after Launch
My Question is bit deeper on the Satellite been put into orbit of GEO .
Recently ISRO Launch GSLV Mark 3 to put into GSO .
After the Rocket is launched and reached the Perigee ( 190 km ) the ...
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1answer
32 views
A dreidel on a spinning table
In the spirit of the holidays.
Let's assume that a dreidel is spinning counter-clockwise at frequency $f$ on a table.
From external point of view, what will I see if I rotate the table clockwise at ...
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1answer
36 views
Will space junk handle itself to an extent?
So suppose that two satellites traveling in opposite directions collide and some bolts are hurdled at higher speeds than either of the bodies were traveling before. Since the junk is traveling at a ...
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1answer
24 views
The shape characteristics of gravitational wells given different masses and spread of objects
I am curious as to research that calculates the shape of gravitational wells, and their limits, and affect on time, for different masses and spread of mass. The actual question is st the end.
For ...
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5answers
121 views
How would the path of a satellite be affected by the gravitational constant decreasing? [closed]
An artificial satellite is moving around the surface of earth. If the magnitude of the gravitational constant starts decreasing at a constant rate, then what would the effect on the path of the ...
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2answers
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How are Quantum Mechanical energy levels related to atom shells?
I'm currently taking Quantum Mechanics in school and I came across a table displaying the following in the given order:
$E_n (\text{energy levels}), g_n (\text{eigen functions})$
$n \ l, [m]$
$E_1, ...
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1answer
51 views
What's the eccentricity of our sun's orbit around the center of the galaxy? [duplicate]
Just thinking about "galactic habitability zones." Is this even a valid question?
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0answers
39 views
A question about almost stationary orbits
For an orbit around the earth with period equal to a sidereal day with eccentricity $e=0$ and inclination $i=0$, the path on earth would be a single point on the equator. I have done some simulations ...
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3answers
98 views
Equation of motion for Central Force problem with repulsive inverse square law
This seems to be a very simple question, but it has been bugging me for days. I have found many material related to this, including the great Goldstein book, but none get quite were I want. I'm ...
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0answers
39 views
Is angular momentum independent of axis (if axis is parallel)?
I have been told this is true for the moon on this question:
Angular momentum of orbiting + rotating body
but I don't understand why it should work. Surely the axis must be chosen such that the ...
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0answers
45 views
The event horizon of a black hole supposes an absolute zero in some field?
Based on the Schwarzschild black hole theory, if the gravitational pull of the singularity were to equalize the energy that a photon has by approaching the event horizon from a special angle, would it ...
