Orbital motion Definition and 40 Threads

In physics, an orbit is the gravitationally curved trajectory of an object, such as the trajectory of a planet around a star or a natural satellite around a planet. Normally, orbit refers to a regularly repeating trajectory, although it may also refer to a non-repeating trajectory. To a close approximation, planets and satellites follow elliptic orbits, with the center of mass being orbited at a focal point of the ellipse, as described by Kepler's laws of planetary motion.
For most situations, orbital motion is adequately approximated by Newtonian mechanics, which explains gravity as a force obeying an inverse-square law. However, Albert Einstein's general theory of relativity, which accounts for gravity as due to curvature of spacetime, with orbits following geodesics, provides a more accurate calculation and understanding of the exact mechanics of orbital motion.

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  1. xpell

    I If Jupiter had a 5th large moon until "recently", would we know?

    Hi! I'm fascinated by the apparent "concentration" of the four large Galilean moons in a barely 1.5 million km "strip", and the vast, "empty" distance to the next moons (moonlets?) Out of a purely aesthetic sense of horror vacui, :wink: I've always wondered if there was at least another Jovian...
  2. E

    Can Sci-Fi Spacecraft Achieve Stable Orbit with Plasma Technology?

    Hi. I'm not expert in physics. Recently I have written an article how a spacecraft will remain in orbit forever. However need review if there is any mistake using formulas or the term escape velocity. Here is it, Layman question: So what will happen if we use sci-fi spacecraft to takeoff...
  3. PeterDonis

    A Puzzle Involving the Moon's Orbital Motion

    This is a puzzle involving the orbit of the Moon around the Earth, based on the well-known story of Newton observing a falling apple and wondering if the same force that made the apple fall could also explain the motion of the Moon. The story goes that Newton considered the following: the...
  4. R

    I How can Kepler's laws be visualized using a simulator?

    Hello, I am loking for some simulator of the solar system where the movement of the planets is represented. I´'m interested in seeing the central force and linear velocity vectors.
  5. M

    B Can Canceling Orbital Motion Improve Rocket Efficiency?

    Would accelerating a rocket in a vector that "cancels" Earth's orbital motion relative to the center of the milky way in some cases improve the energy efficiency of a rocket for a given amount of change in velocity relative to the earth?
  6. R

    Finding the period of the satellite's orbital motion

    Homework Statement I want to find the period of the satellite. Homework Equations mg = mv^2/r The Attempt at a Solution I derive the equation mg = mv^2/r v = sqrt(gr) v = ωr and ω = 2π/T T = 2π/ω = 2πr/v Then, T = 2πr/sqrt(gr) But the answer is 2πr/R * sqrt(r/g). I don't know why? Is...
  7. D

    Mercury's orbit according to Classical VS Modern Physics

    Hello, I'm a high-school student and I was assigned to do this kind of a paper as a senior (one of the requirements of graduating is a short monograph on a subject of interest.) My topic includes an analysis of Mercury's orbit using Newton and Kepler's equations and comparing the predicted...
  8. PlanetGazer8350

    Calculate iron container acceleration in railgun system on the Moon

    Having a cylindrical iron container with wall thickness of 20 cm, and a total weight of 500 tons when filled with its cargo, how would you be able to calculate its required voltage and current input in a vertical railgun system (relative to the Moon's surface), with an exit acceleration of...
  9. J

    Writing: Input Wanted Eleven Inner Planets--What Will Earth's Ice Ages Be Like?

    A Milankovitch cycle is defined in Universe Today as "a cyclical movement related to the Earth’s orbit around the Sun." There are three elements to a Milankovitch cycle that affects the amount of solar heat and with it, the Earth's climate: Eccentricity (Orbital Shape)--The elliptical shape...
  10. J

    B E=0. What Does That Mean for the Seasons?

    Currently, Earth's eccentricity (orbital shape) is 0.0167086. Zero is a perfect circle whereas One is parabolic escape orbit and any greater becomes a hyperbola. And in the theory of the Milankovitch cycles, Earth's eccentricity varies between 0.000055 and 0.0679 over a period of 100,000 years...
  11. Phys_Boi

    B Calculating the Effects of Velocity and Gravity on Orbital Motion

    So if an object has a velocity expressed by the vector <-3,0> and is being accelerated toward another object with the vector <-1,-2>... After one second, the object will have moved from (0,0) to (-4,-2) - calculated by adding the vectors.. My question is after the first second does the object...
  12. A

    How Does Rosetta Maintain Orbit Around a Low-Gravity Comet?

    Hi All, I know that Rosetta was orbiting around 67P/Churyumov–Gerasimenko. This asteroid has extremely low gravitational force acting on Rosetta. I believe that if the celestial body is heavy (mass), then there would be greater gravitational pull on the satellite and the orbital speed of it's...
  13. A

    Velocity of Electrons: Orbital Motion & Velocity Explained

    What is the relation between the orbital motion and velocity of electron? Do the electrons close to the nucleus have high velocities or those who are in higher orbits?
  14. V

    Centripetal force and orbital motion....

    Hi, The force of gravity is the centripetal force when an object is in motion. But in projectile motion, where the speed is not enough to keep it in orbit, could the force of gravity be equated to centripetal force? I'm trying to understand if all types of curved motion can be explained by...
  15. P

    Why is black hole photon sphere outside the event horizon?

    Homework Statement I am preparing a report on black holes and I recently learned about a phenomenon I was previously unaware of: the photon sphere of a black hole. While reading an article on said occurrence (I have now confirmed this on multiple sources) the photon sphere which is the minimum...
  16. X

    Magnetic Dipole due to an electron's orbital motion

    Homework Statement Select all of the following which are possible combinations of Lz and θ for hydrogen atoms in a d state, where Lz is the z component of the angular momentum L, and θ is the angle between the +zaxis and the magnetic dipole moment µℓ due to the electron's orbital motion...
  17. O

    Is Kinetic Energy Equal to Negative Potential Energy in Circular Orbital Motion?

    Hey, so I have a question about motions of planets and their energy basically. When we have a circular orbit, why is it that the kinetic energy is just the opposite of potential energy? (Assuming it's a closed orbit) Like if we have U = something, than the kinetic energy T = -1/2U? This would...
  18. 2

    How can you tell what kind of orbit a body will have?

    Is there a way of telling whether the orbit of a body around another, or rather of both around their centre of mass, will give the object in question a circular, elliptical, hyperbolic or parabolic orbit? Thank you!
  19. T

    Could a Tidal Lock Cause the Earth to Stop Rotating?

    So my co-workers and I have had a dispute after hearing a podcast on NPR about Earth's rotation. One question was about what would happen if one side of the Earth always faced the sun (tidal locked) and another question was about what would happen if the Earth stopped rotating. From what I've...
  20. CaptainSiscold

    Angular kinematics: determining satellite orbital radius

    So, I'm working on my semester finals for my high school physics class, and I've run across a problem that has me stumped. I've included the pertinent material below. Homework Statement A rocket with a mass of 2kg and traveling at 14,008.34 meters/second loses 10% of its velocity as finishes...
  21. L

    Deriving Orbital Motion from Collisions in Travel along Chords

    Homework Statement Inscribe N chords of equal length within a circle of radius r. A body of mass m travels at constant speed v along the chords and is perfectly reflected in each collision with the circle (there is no momentum change tangent to the circle). Show that the radial momentum change...
  22. H

    Orbital motion electron (quantum)

    Homework Statement Excited sodium atoms emit two closely spaced spectrum lines called the sodium doublet with wavelengths 588.995 nm and 589.592 nm. (a) What is the difference in energy between the two upper energy levels (n=3 l=1)? (b) This energy difference occurs because the electrons...
  23. H

    Where Did I Go Wrong in My Analysis of Orbital Motion?

    Hi, I stumbled upon this while working on a problem on my physics homework. I still want to solve the problem myself if possible though so I won't post it here, instead, I'll post what is confusing me. Consider orbital motion with potential U(r), where U(r) is any arbitrary function of r. I...
  24. C

    Is there any relation between orbital motion and spin motion?

    hi guys, i have a question about the orbit-spin relationship of the celestial objects. for example in our solar system i understand the orbital period becomes lengthy for the planets more distant than the sun, it's logical, but what happens with their spinning motion..? i don't understand why...
  25. Z

    Formula for simulating orbital motion (2D)

    Hello. I'm new on this forum and I hope I'm posting this in the right place. This is not for a homework assignment but a spare-time project I'm working on. Homework Statement The goal with this project is to make a simple program that simulates an object that orbits a single fixed point...
  26. B

    How Does the Mass of the ISS Affect Its Orbital Motion?

    I'm not asking for you to do my homework but can you help me on it?! I have no idea how to even attempt it. Any help would be greatly appreciated! The International Space Station (ISS) just celebrated its 10th anniversary of human habitation. During that time it has been orbiting the Earth...
  27. J

    Help with satellites and planets orbital motion

    A Martian civilization is attempting to develp the capabilities for space travel. They have built a prototype satellite with a mass of 578kg that they plan to put in orbit Mars a distance of 602km above the surface of mars. A) Using the data provided, calculate the orbital velocity of the...
  28. S

    Understanding Orbital Motion and Energy Levels in Hydrogenic Atoms

    I am analysing the motion of the electron and the nucleus of a hydrogenic atom. I know that the two particles, so to speak, rotate their common centre of mass and that the two-body system is identical with respect to the predictions (e.g. energy) borne out by the system to a one-body system of...
  29. G

    Exploring Orbital Motion Around Earth

    orbiting earth! Hope iposted this question in the right spot!. If i launched something in space and then stopped its forward momentum wouldnt the Earth gradually move away from it and pick it up again so to speak..a year later?
  30. J

    How long until the planets collide?

    Homework Statement Two planets of masses m_1 and m_2 with radii r_1 and r_2 respectively are orbiting their common center of mass at some initial distance x_0 from each other with angular velocity \omega_0. Find the amount of time it takes for these planets to collide. Homework Equations...
  31. K

    Electron Orbits and Nuclei 2- Rotation vs Orbital Motion

    1-is electron orbit about the nucleus ? 2-is there is different between rotation and orbit? thanks in advance
  32. M

    How Do You Solve Complex Orbital Motion Mechanics Problems?

    Looking over past problems and these types of ones always bothered me. Really need the help here guys. A particle moves in a plane, projected from an apse, with speed SQRT(t/b), at a distance b, under a repulsive force t(u)^2 + 2bt(u)^3. Show the motion is u = (-1/3b) + (4/3b)COS(SQRT(3)O)...
  33. P

    How Does the Decreasing Mass of the Sun Affect Earth's Orbital Radius?

    1. The mass of the sun is decreasing as dM/dt=-constant .M Find [dr/dt]/r for the earth Homework Equations [b]3. I tried using M=M0-alpha. t and then separating the variables in the equation GMm/r^2=mdv/dt. I don't knot the right way to solve this. Plz tell me how to solve this...
  34. andrevdh

    Understanding Orbital Motion with Polar Coordinates

    I'm a bit unclear about the description of orbital motion in a plane by using the polar coordinates (r,\theta). This coordinate system changes its orientation in the inertial reference frame, that it is rotating as the orbiting object moves along its path. In the derivation of the equations of...
  35. B

    Question on Orbital Motion and Conservation

    To make the moon deviate from it's straight line path requires a force and I assume this force requires energy. Considering the mass of the moon and the billions of years it has been orbiting the Earth this seems like a tremendous amount of energy expended. With regard to the conservation of...
  36. R

    Newton's 2nd Law and Orbital Motion

    Here's the problem...unfortunately I don't remember much about orbital motion. I'm a bit stuck on where to begin. If somebody could give me a little advice on how to tackle this problem I would appreciate it. Recall that the magnetic force on a charge q moving with velocity v in a magnetic...
  37. I

    Newtons Laws of gravitation, Keplers law, & Orbital Motion?

    Can anyone give me a clear and good explanation of Newtons Law of Gravitation, Keplers Law & Orbital Motion.
  38. C

    Orbital Motion Help: Calculate Altitude of Spacecraft

    Hi guys and gals I have been given this question and have spent so far around 4 hours pondering calculating researching and reading and have got no where except into a large state of confusion! Its probably really really simple but i just can't seem to get logical answers and now i have...
  39. S

    Discover the Relationship Between Escape Speed and Circular Orbit Speed

    Show that the escape speed from a planet is related to the speed of a circulat orbit just above the surface of the planet by Ve = square root(2Vc), where Vc is the speed of an object in the circular orbit. I'm looking at GMem(object)/r^2 = m(o)v^2/r But I do not know if this equation will...
  40. Loren Booda

    Does the MBR display orbital motion relative to us?

    Can we discern any movement by the microwave background perpendicular to its expansion?
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