What is Orbital speed: Definition and 43 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. Kyuubi

    Solving Orbital Speed with Energy & Angular Momentum Conservation

    I've already solved the orbital speed by equating the kinetic and potential energy in the circle orbit case. $$\frac{1}{2}mv^2 = \frac{1}{2}ka^2.$$And so $$v^2 = \frac{k}{m}a^2$$Now when the impulse is added, the particle will obviously change course. If we set our reference point in time just...
  2. T

    Orbital speed variation as a planet orbits the Sun

    Summary:: At what distance from the Sun will the speed of the planet be equal to the average orbital speed? I'm not sure where to place this question, please move it in the right thread. [Mentor Note -- thread moved from the technical forums, so no Homework Template is shown] At what...
  3. pobro44

    Angular and orbital speed at perihelion

    Hello to all good people of physics forums. I just wanted to ask, whether the angular and linear (orbital) speed in perihelion of eliptical orbit are related the same way as in circular orbit (v = rw). If we take a look at the angular momentum (in polar coordinates) of reduced body moving in...
  4. N

    Orbital speed of an object in a circular orbit

    Homework Statement Consider a central force is attractive but which passes through the force center. In other words, consider an orbit of radius a which is centered at (a,0), with the force center at the origin c.) Suppose the speed at the apogee is v0 Find the oribital speed v as a function of...
  5. K

    Is F = m*(v^2/r) true when the orbital speed increases?

    In circular motions, one can measure the NetForce on an object with this formula: ΣF = m*v^2/r. But is this formula valid even if the orbital speed of the object is constantly increasing (or constantly decreasing)?
  6. Strange design

    I Observing Orbital Speed of stars within Galaxies

    Can someone point me to a resource that describes, or describe, how the orbital speed of stars within galaxies are observed and measured? I'm struggling with how these values can be attained with any confidence in their accuracy. Thanks :)
  7. alybtd

    Orbital vs. Angular Speed: What's the Difference in Circular Motion?

    Is there a difference between orbital speed and angular speed when an object or star is considered to be in a circular motion around another?
  8. T

    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...
  9. D

    Calculating Planet Mass from Stellar and Orbital Speed

    Homework Statement Stellar mass 3.8 x 10^30 kg Star's orbital speed: 90 m/s Planet's orbital speed: 95,000 m/s Whats the mass of the planet in kilograms [/B]Homework EquationsThe Attempt at a Solution
  10. I

    Redshift, Earth's orbital speed, and the speed of light

    The Earth is moving around the Sun at around 30km/s, a change of 60km/s over the course of the year. Presumably, measurements of the speed of light would show a redshift up to ±30km/s? Are redshift measurements this accurate? Likewise, the speed of the Solar System around the Milky Way, is...
  11. K

    What is Upiter's speed when closest to the sun?

    A hypothetical planet Upiter orbits the sun. Upiter's semi-major axis is 5.2 AU. The mass of Upiter is .001 that of the sun. The eccentricity is 0.2. For this problem, ignore the other planets. d. Compute Upiter's speed when it is closest to the sun. I believe the equation I use for...
  12. E

    Orbital speed - faster is closer?

    I am very confused about the fact that, for example, Pluto moves around the Sun much slower then Earth and is also much further from the Sun, so its period is way longer that that of Earth's.. if I want to increase orbital height, I add speed to the object I want to raise, no? How come...
  13. L

    Gravitational potential energy, orbital speed, binding energy.

    Homework Statement a satellite having a mass of 1800 kg orbits the Earth at a distance of 6.3 x 10^5 m above the surface find the gravitational potential energy of the satellite while in orbit, the orbital speed and the binding satellite. The Attempt at a Solution gravitational potential...
  14. N

    Effect of Tangential and Normal Forces on Orbital Velocity of Planets

    Homework Statement What effect will the tangential component of force have on the velocity of the planet? What effect will the normal component of force have on the velocity of the planet? Homework Equations The Attempt at a Solution 1. Since it is parallel to the direction of velocity, maybe...
  15. A

    Angular speed vs. Orbital speed

    Homework Statement Consider a year to be precisely 365 days. Determine the angular speed of the Earth about the sun. If the Earth's mean distance from the sun is 1.496x1011 meters and our orbit is circular, determine our orbital speed about the sun. Homework Equations ω=Δθ/T, where ω is...
  16. L

    Calcuate Orbital Speed (without using distance)

    How would I go about calculating the orbital speed of a planet without using the distance of its path. In other words, only using the motion around the plane of ecliptic? My first thought was using the angle of the path somehow, but I'm a bit stumped here. Thanks for any input!
  17. M

    Calculating Orbital Speed and Period of a Weightless Satellite

    [b]1. Homework Statement : An artificial satellite revolves about the Earth at height H above the surface. If the radius of the Earth is R, calculate the orbital speed and the orbital period such that a person in the satellite will be weightless. Homework Equations The Attempt at a...
  18. S

    If Earth's orbital speed doubled, would its mass and gravity double?

    I am not all that great at mathematics or physics or anything like that, though it does interest me a great deal and I am just trying to better understand the theories, so please bare with me here. I have read that the closer an object gets to traveling at the speed of light its mass...
  19. P

    ** Question related to Orbital speed of star, Keep getting *10^4 to high?

    *Please Help* Question related to Orbital speed of star, Keep getting *10^4 to high?? Homework Statement A star has a mass of 2.2*1030kg, there is a planet of mass 4.5*1027kg orbiting it at a distance of 3.1*1011m (also told that it has a "period of wobble" of 9.2*107s due to the orbiting...
  20. E

    What is the potential of tethers for space exploration and satellite propulsion?

    How fast would a satellite need to travel to mantain an orbit of 30 statue miles above sea level?
  21. S

    What is the orbital speed of a satellite at a radius of 34 km?

    Homework Statement A satellite is in orbit around a planet. The orbital radius is 34 km and the gravitational acceleration at that height is 2.3 m/s^2 What is the sattelites orbital speed in m/s
  22. D

    Quick question on orbital speed of satellite

    Homework Statement The polar orbiting satellite NOAA-N was launched in May 2005. The satellite is now moving in a circular orbit above the Earth's surface at an altidude of 870 km. THe mass of the Earth is 5.97 x1024kg and its mean radius is 6.38 x106m. Show that the orbital speed of the...
  23. M

    Calculating Orbital Speed and Period for a Satellite in Circular Orbit

    Homework Statement A satellite of mass 600kg is in a circular orbit about the Earth at a height above the Earth equal to the Earth's mean radius. Find: a) the satellite's orbital speed b) the period of its revolution c) graviational force acting on it Homework Equations a) v^2 =...
  24. M

    Finding ortibal period and orbital speed PLEASE HELP

    Homework Statement GPS (Global Positioning System) satellites orbit at an altitude of 2.6×107 . Find the orbital period. Find the orbital speed of such a satellite. Homework Equations I would like to know how to approach this. I don't know where to start w/o other figures. The...
  25. M

    Satellite orbital speed homework

    [b]1. A satellite has an orbital speed of 4.2 x 10^3 m/s. What is its altitude above Earth's surface? mass of earth= 5.98x10^24kg radius of Earth = 6.38x10^6m [b]2. acceleration and force are both centripetal a=(v^2)/r F=ma possibly v^2=(Gmg)/r [b]3. Need help with algebra h=...
  26. R

    Orbital Speed: Earth vs Moon - How Does Altitude Affect Orbital Velocity?

    Just can't get my head around this one. If at 100Km high above Earth the orbital speed to maintain altitude is X, then what would the speed be for the same object around the moon? Since gravity of the moon is smaller then earth's? I assume the orbital speed would need to be less?
  27. C

    How Do You Calculate Orbital Speed in Different Galactic Density Models?

    Orbital Speed of a Star - Please Help! Homework Statement Calculate \Omega(r) and v(r) for the following density models: (a) all the mass M is at the center of the galaxy; (b) a constant density adding up to a mass M(R0) at the Sun’s orbit and no mass beyond. Homework Equations...
  28. C

    How Do You Calculate Orbital Speed in Different Galactic Density Models?

    Homework Statement Calculate \Omega(r) and v(r) for the following density models: (a) all the mass M is at the center of the galaxy; (b) a constant density adding up to a mass M(R0) at the Sun’s orbit and no mass beyond. Homework Equations M(r) = v(r)2r/G The Attempt at a...
  29. T

    Calculation of orbital speed for given eccentricity

    Hi, I am trying to work out, for a given eccentricity,a known planet mass and a known value for the semi major axis is there a formula to work out the orbital speed of a planet around a central star? I have looked around online with not much success and was wondering if anyone could point me...
  30. A

    Calculating Orbital Speed of a Satellite Orbiting Jupiter | Step-by-Step Guide"

    Please help asap! Orbital speed Homework Statement A satellite is placed in orbit 5.19x105m above the surface of Jupiter. Jupiter has a mass of 1.90x1027kg and a radius of 7.14x107m. Find the orbital speed of the satellite. Answer = m/s Homework Equations v = sqrt [GM/r]...
  31. W

    How Do You Calculate the Orbital Speed and Period of a Satellite?

    Homework Statement the solar maximum mission satellite was placed in a circular orbit about 150 miles above earth. Determine (a) the orbital speed of the satellite and (b) the time required for 1 complete revolution Homework Equations The Attempt at a Solution
  32. U

    Calculating Orbital Speed: Jupiter & Earth Orbit Time

    ok just a couple orbital questions I forget the equation that needs to be used and do not have my textbook with me so if anyone knows the equation for finding orbital speed that would be great! 1. calculate the speed of a satellite in orbit 9.5 x10^3 km above jupiter. radius of Jupiter =...
  33. X

    Solving the Astronauts' Orbital Speed & Period Around the Moon

    Hey guys, I got the following problem. It seems east, btu I still have no idea how to get started on this one:frown:
  34. E

    Calculating Orbital Velocity for a Satellite Orbiting Earth

    Can you find the orbital velocity of a planet which a satellite has to obtain in order to revolve around the planet with this formula: v = \sqrt{\frac{Gm_E}{r_E}} G = gravitational constant 6.67*10-11 mE = Mass of a planet rE = the radius of the orbit rE = h + r h = height of the...
  35. J

    What is the Orbital Speed of a Satellite at 7000 km Altitude?

    Homework Statement A satellite is in circular orbit above the Earth at an altitude of 7000 km. What is the orbital speed of the satellite?Homework Equations Well, knowing that the mass of Earth of 5.98 X 10^24 kg And the radius of Earth is 6.38 x 10^6 m What equation do I start with here...
  36. Holocene

    Orbital speed of stars within galaxies?

    I have read some information, from various sources, pertaining to the orbital speed of stars about the center of galaxies, and some of it appears to be conflicting. Some sources claim that the stars closer to the galactic center orbit faster, while those father out, orbit slower. This of...
  37. R

    Calculating the Orbital Speed of Mars: An Easy Guide

    orbital speed of mars! help!? Mars is 230 million km from the sun. It completes one orbit in a period of approximately 687 days. Calculate the orbital speed of Mars in mph. OK so gave me the formula which 2*pi*r/ Period r= distance from the planet to the sun. and cirmumference = 2*pi* r...
  38. B

    Calculating Earth's Orbital Speed Using Star Spectra

    How can the earth’s orbital speed be determined from observations of the spectrum of a star? Thanks
  39. R

    Orbital Speed of Earth: Calculating the Speed of Earth's Orbit Around the Sun

    Orbital speed of Earth! help! The Earth is 150 million km from the sun. IT completes one orbit in a period of approximately 365.25 days. Calculate the orbital speed of Earth in mph? OK guys so they give me the formula which is 2*pI*r /Period r= distance from the planet to the sun. and...
  40. J

    Orbital Speed calculation using conservation of Energy

    An unmanned spacecraft moves in a circular orbit with speed v around the moon,observing the lunar surface at an orbital radius of R=1790 km.The period of the orbit is T.Unfortunately, an electrical fault causes an on board thruster to fire, reducing the speed of the spacecraft by \Deltav=5...
  41. L

    Understanding Orbital Speed and Energy Dynamics

    I have a question about orbital speed. Imagine a shuttle moving in an orbit near the Earth surface, its total energy is "-GMm/2r", so its total energy is directly proportional to -1/r In order to spiral into another orbit of smaller radius which mean it would have a larger angular speed...
  42. S

    The Ground State Orbit of a W+73 Atom: Is It Bohr-rific?

    The nucleus of Tungsten conssits of 74protons and 110 neutrons. SUppose all of the electrons were stripped off, but one, leaving a W+73 atom. Using the Bohr idea of the atom (not anything else!) How much energy nrequired to remove this last electron from orbit?? The energy of the elctron...
  43. D

    Earth's Orbital Speed Around the Sun

    The Earth has an orbit of radius 148 million km around the sun. What is the speed of the Earth on this orbit? dont know how to do it i have used a couple of different formulas and haven't gotten it right can anyone help?