# What is Orbital velocity: Definition and 48 Discussions

In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one object is much more massive than the other bodies in the system, its speed relative to the center of mass of the most massive body.
The term can be used to refer to either the mean orbital speed, i.e. the average speed over an entire orbit, or its instantaneous speed at a particular point in its orbit. Maximum (instantaneous) orbital speed occurs at periapsis (perigee, perihelion, etc.), while minimum speed for objects in closed orbits occurs at apoapsis (apogee, aphelion, etc.). In ideal two-body systems, objects in open orbits continue to slow down forever as their distance to the barycenter increases.
When a system approximates a two-body system, instantaneous orbital speed at a given point of the orbit can be computed from its distance to the central body and the object's specific orbital energy, sometimes called "total energy". Specific orbital energy is constant and independent of position.

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1. ### A Exploring Orbital Velocity vs RMS of Eddy Velocities

Is there a difference between the orbital velocity of an eddy and the root mean square of the velocity fluctuations? I'm particularly interested in understanding the eddy turnover time of the largest eddies in a turbulent flow, which is given by the characteristic eddy size and the...
2. ### Calculation of orbital velocity -- Geometrical solution

Hello, I would like to calculate the orbital velocity using the geometrical way of reasoning. But I have a hard time to understand and apply some basics into my calculations. The reasoning is pretty simple. After some time: dt ,the particle travels the distance: Vtot1 * dt = R*sinθ (see the...
3. ### Orbital velocity of a craft at 4km above the Moon's surface

What would be the orbital velocity of craft at 4km above moon surface? Assume a mass of 1,000,000 lb, US.
4. ### I Planet mass vs. orbital period

I recently read a short summary of Kepler 11 and the Kepler Mission. I understand that the orbital period of a planet is a function of its velocity and distance from the star, and the mass of the star will also factor in. Question: Is the mass of the planet also a factor? In other words, does a...
5. ### Regarding the radius in the orbital velocity

Would the velocity of a body which is orbiting another body change due to its radius to the center of gravity? If so, why? A body which moves passed a planet and starts orbiting it should have the same velocity it had before ,regarding the fact that it is orbiting a planet. Also, gravity isn’t...
6. ### Find the speed of a satellite at a distance R from Earth

Homework Statement Gravitational force exerted on mass m is GMm/r^2 2. Relevant equations Orbital velocity at distance R from Earth = ##\sqrt gR## Escape velocity = ##\sqrt 2gR## gR = GM/R Fc = mV^2/R F =m.aThe Attempt at a Solution 1) express acceleration of gravity in terms of G, M , and R...
7. ### Gravity, friction and tangential velocity

Hi everyone, Me and a friend discussed a problem relating to a rotating reference frame, and somehow got to this question which we can't fully figure out, or maybe we are missing something. so, here goes: On Earth's equator, our tangential velocity is ~1700 km/hr. A satellite orbiting right...
8. ### Can you find orbital velocity from circle equation y^2+x^2=r^2?

Maintaining R as the constant hypotenuse in the triangle formed by x and y coordinates in a 'perfect' circle, r2=x2+y2 r2=x2+y2 So knowing that in 9.8 metres above ground it will take 1 second for an object to fall, I tried to find how many metres in the X direction an object must cover in 1...
9. ### Orbital velocity of a baseball

Homework Statement If you stand on the surface of a spherical asteroid of mass 1.12*10^17 kg and radius 20km, how fast must you throw a baseball to put it into orbit at 1.0 m above the surface? Homework Equations PE=KE GMm/r^2 = 1/2mv^2 G = 6,67*10^-11 The Attempt at a Solution I rearranged...
10. ### B What does "orbital velocity" mean in a quantum setting?

Hi. I once heard somewhere that atoms of heavy elements like gold get unusual properties such as gold's yellow color due to "relativistic contraction" of the orbitals due to their high "orbital velocity". But what on Earth does orbital velocity mean in quantum mechanics? These are quantum...
11. ### B Calculating Orbital Velocity in 2D

Hi! Imagine a planet is alone in a two dimensional universe. It has a mass mp. Suddenly, the planet's moon appears out of nowhere. It appears with a distance r from the planet, has a mass mm and velocities vx in the x-direction and vy in the y-direction. The distances rx and ry are also known...
12. ### 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. ### Orbital Velocity: Why Mass Doesn't Matter

why orbital velocity of a satellite is independent of mass?
14. ### Derivation of orbital velocity formula

Is there some mathematical derivation for calculating the orbital velocity based on altitude and acceleration without using calculus? I thought of equations of motion, but I always get problems. Is there a way to derive it using laws of gravitational potential and kinetic energy ? Are the...
15. ### Orbital velocity and radius for satellite

Homework Statement A geostationary satellite is to be placed to view the far side of the moon. How far away should it be placed from the center of the Earth and what velocity should it travel in order to maintain its orbit? (Considering the moon and Earth as one entity and solve for the center...
16. ### Planetary Orbits & Orbital Velocity

Hi pf, please could someone explain why the orbital velocity increases as you get closer to the sun. I treated the situation like circular motion and did a load of calculations. I calculated the orbital velocity of all 8 planets and then the force between each of the eight planets and the sun. I...
17. ### How do I calculate orbital height from orbital velocity?

I'm sorry if this isn't astrophysics but I didn't know what else to post on. So I play this game called Kerbal Space Program, and I've recently been trying to calculate the delta v needed to launch my rockets and spaceships from all the planets and moons in the game. I learned how to calculate...
18. ### Lagrange Point and orbital velocity

When considering the Lagrange point 1 in the Sun/Earth system, Does Lagrange Point 1 have any orbital velocity around Earth? I suspect a body at L1 has no orbital velocity around earth. But consider the Earth's position 6months later when it is opposite the sun. The Lagrange point would also...
19. ### Vis-viva equation (Orbital Velocity) with massive satellite?

Wikipedia states that "In the vis-viva equation the mass m of the orbiting body (e.g., a spacecraft ) is taken to be negligible in comparison to the mass M of the central body." I'm wondering how the velocity is determined if the satellite's mass is non-negligible. For example, in a binary...
20. ### Electron orbital velocity in hydrogen atom?

Are there any actual numbers for electron orbital velocity in hydrogen atom?
21. ### Calculate the orbital velocity in a geostationary orbit

Homework Statement Calculate the orbital velocity in a geostationary orbit (the circular orbit around the Earth which has a period of 24 hours) and show that its radius is approximately 40,000 km. A satellite is to be inserted into a geostationary orbit from an elliptical orbit with perigee at...
22. ### Equations for Apollo Spacecraft Orbital Velocity & Moon Escape Velocity

Look for help on these equations. Any help will be greatly appreciated. Thanks so much! :) The Apollo spacecraft must be traveling at what velocity in order to remain in a 110 kilometer orbit around the moon? The magnitude of the Apollo’s orbital velocity can be computed from the laws of...
23. ### Please check what I've derived. Involves force and orbital velocity.

Basically, I'm trying to come up with a function that determines the amount of force need to keep an object in a stable circular orbit if it were to suddenly lose altitude due to a collision or what not. Basically required force as a function of orbital radius. Here's what I've come up with...
24. ### Schwarzschild/post-Newtonian circular orbital velocity

The post-Newtonian expansion at the first post-Newtonian 1PN level under Schwarzschild conditions, a test-body in a spherically symmetric gravitational field, gives the following expression for the gravitational acceleration of the test-body: \frac{{\rm d}\bar{v}}{{\rm...
25. ### Mass of Jupiter given a Moon's mass, orbital velocity and distance.

Hello all, been meaning to make an account here and participate but haven't been around to it. So sorry that my first post is asking for homework help! :| Homework Statement The planet Jupiter has a moon Europa (m = 5x10^22kg) that is orbiting at a velocity of 14,000m/s at a distance of...
26. ### Trying to find orbital velocity based off of height

Homework Statement A Titan IV rocket has put your spacecraft in circular orbit around Earth at an altitude of 397 km. What is your orbital velocity? Give your answer in m/s.Homework Equations http://as370.socialhwk.com/engr370i/ch04/ch4_3/IMG00015.GIF...
27. ### Orbital Velocity Calculation for an Asteroid at Perihelion

Homework Statement If calculating the orbital velocity of an asteroid at perihelion I use: Vp = {GM/a ((1+e)/(1-e))}^0.5 Is the G the gravitational constant G = 6.67x10^-11 Is M the mass of the sun = 1.988x10^30 kg Is 'a' the mean distance of the asteroid from the Sun in metres/km/AU ...
28. ### Orbital velocity and rotational velocity

Hi Is "orbital velocity" supposed to be the same as "rotational velocity"? it seems that a "rotation curve" is supposed to plot the rotational velocity of a star, but then some articles e.g. http://en.wikipedia.org/wiki/Galaxy_rotation_problem claim "orbital speed" is plotted. The equation...
29. ### Addition of grav potentials / Orbital velocity

The Attempt at a Solution I think I may of been too general with the volume in finding M_0 I'm assuming r_0 = r_M although I'm not sure why different notation is used thougj http://imageshack.us/photo/my-images/3/gravscan.jpg/
30. ### Orbital Velocity due to a Dark Matter Halo

Homework Statement I am struggling to calculate the gravitational force from a dark matter halo given that its density is given by ρ(r) = ρ0r02/r2. Once i have found the force i plan to equate it to the centripetal force, F = mv2/r, to find the velocity, v. Homework Equations Density...
31. ### Help Determining Orbital Velocity about the Center of Mass

Hey, so I'm new to Physics Forums as a registered member, but I've been checking this site out for what seems likes years. Homework Statement Locate the center of the mass of the Earth-moon system with respect to the center of the Earth, and then find the orbital velocity of the Earth...
32. ### What is the orbital velocity at pericenter and apocenter

One way of lifting a satellite into geosynchronorous orbit is to use the space shuttle to lift it into a circular, low-earth orbit(h=300km) and then use a booster rocket to place the satellite on a hohmann transfer orbit up to a circular geosynchronous orbit. what is the orbital velocity of the...
33. ### Is it possible to find orbital velocity depending on time?

A satellite is in orbit around earth, (you know G, mass of earth, etc. but NOT the radius) is it possible to find orbital period?
34. ### Calculating Orbital Velocity Ratios for Planets A and B

Planet A and planet B are in circular orbits around a distant star. Planet A is 8.5 times farther from the star than is planet B. What is the ratio of their speeds Va/Vb This problem seems very simple, thought i could just use F=1/r^2, find the difference in forces, which would also be the...
35. ### Orbital Velocity Homework: Find Velocity of Geostationary Satellite

Homework Statement Basically says that a geostationary satellite requires a distance of 35 900 km above Earth's surface. I need to find its orbital velocity. Homework Equations The Attempt at a Solution I find the circumference of the orbit = 225566.3525km then change units to...
36. ### Exploring Orbital Velocity: Significance and Applications

I am fairly new to astronomy, having just finished a course this past semester in high school, and I have a question about orbital velocity. Now, I know that the event horizon is the boundary at which the escape velocity is equal to the speed of light, but is there any significance to the...
37. ### I am confused about the orbital velocity

Hello, We know that to calculate the orbital velocity we use the relation : Vo=2* pi* r /time of one cycle but if we want to calculate the orbital velocity when a body moves from the point a to the point b on a circular path we use the relation : Vo = The line segment ab / time...
38. ### Solve Orbital Velocity Equation: V=sqrt((g*R^2)/r)

I have a homework problem that involves the equation v=sqrt((g*R^2)/r) I am confused as to where this equation comes from. I know that Vcirc = sqrt((GM)/r) and Vesc = sqrt((2GM)/r)
39. ### Can You Achieve a Circular Orbit with Non-Perpendicular Launch Velocities?

If you are at the distance R from a planet and you want to achieve a circular orbit your velocity must be Sqrt[Gm/R] perpendicular to the radius vector. But what if you launch at an angle (ie no longer perpendicular to the radius)? Is it still possible to achieve a circular orbit if the...
40. ### Orbital Velocity vs Mass and Orbital Velocity vs Radius

Homework Statement Graph the relationship between the speed of a satellite orbiting a large mass in uniform circular motion. Also I need to learn how to properly write proportionality constant and proportionality equation. Homework Equations in the equation below, m is the mass of the larger...
41. ### About the Earth's orbital velocity

i want to know if the Earth change its orbital velocity along the day? as i heard that due to its elliptical shape the distance between the Earth and the sun slightly change during the day (increase then decrease again) ,so the orbital velocity also has to change to compensate this change in...
42. ### Calculating orbital velocity at periastron

Homework Statement -Suppose you have traveled to Sirius B with its radius of 5,842,200 m and mass of 1.945 x 10^30 kg. You are traveling in a spaceship 100 meters long. After arriving at close to the speed of light, you slow your spacecraft down to a velocity of only 43.19km/sec at a...
43. ### How To measure Moon Orbital Velocity ?

Im doing a school project where we need to come up with an accurate way to measure the moons orbital velocity with an experiment... My plan was to find the radius of the moons orbit, then its period, and based on a distance over time find its velocity. However i realize I am making a serious...
44. ### Orbital Velocity - Satellite

Homework Statement A science group put in a satellite of mass m kg into a circular Earth orbit of radius r. The orbital velocity it needs to remain in this orbit is v. They now put another satellite into a similar orbit at the same altitude. Its mass is 3 times m. What orbital velocity would...
45. ### Wave orbital velocity components

I am having trouble with the equation below for the U component of the orbital velocity in the x direction for a particle in a wave. I have the encountered data and therefore the static data also. I am wondering if I should use the encountered wave number, k, or the static one? If I use the...
46. ### Can a Particle Reach Light Speed at r=3M in a Schwarzschild Black Hole Orbit?

I understand that light can be in an unstable orbit at Schwarzschild radial coordinate r=3M (geometric units) around a Schwarzschild black hole. I also understand that the local* circular orbital speed of a massive particle around the hole is v_o = r\frac{d\phi}{dt} =...
47. ### Orbital Velocity of Mercury

What is the magnitude of the orbital velocity of the planet Mercury (orbit radius =5.79 * 10^{7} {km}, orbital period = 88.0 days)? Ive been trying to solve this using this equation v=(2pi(57.9*10^9m))/(7.6*10^3)s but it is not coming out right...the numbers in the equation are the units in...
48. ### Discover the Essential Orbital Velocity for Stable Earth Satellite Orbit

I don't know how to answer this question without a given altitude, but since one isn't given then I probably don't need one. Any ideas? Determine the minimum velocity an Earth satellite must have in order to purse a stable orbit without falling to the ground.