What is Gravitational field: Definition and 369 Discussions

In physics, a gravitational field is a model used to explain the influences that a massive body extends into the space around itself, producing a force on another massive body. Thus, a gravitational field is used to explain gravitational phenomena, and is measured in newtons per kilogram (N/kg). In its original concept, gravity was a force between point masses. Following Isaac Newton, Pierre-Simon Laplace attempted to model gravity as some kind of radiation field or fluid, and since the 19th century, explanations for gravity have usually been taught in terms of a field model, rather than a point attraction.
In a field model, rather than two particles attracting each other, the particles distort spacetime via their mass, and this distortion is what is perceived and measured as a "force". In such a model one states that matter moves in certain ways in response to the curvature of spacetime, and that there is either no gravitational force, or that gravity is a fictitious force.Gravity is distinguished from other forces by its obedience to the equivalence principle.

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  1. O

    Calculate Earth's Gravitational Field at the Moon

    The Moon's mass is 7.34x10^22 kg, and it is 3.8x10^8 m away from Earth. Earth's mass is 5.97x10^24 kg. (a) Calculate the gravitational force of attraction between Earth and the Moon. I already did that. It's 2.01e+20. (b) Find Earth's gravitational field at the Moon. This is the part I'm...
  2. B

    Gravitational Field Difference on body near a black hole.

    Homework Statement This is not a homework problem per se, but more of boredom, and curiosity. I was trying to calculate the gravitational field difference on a human body if it were near a black hole. Used Newtons universal law of gravitation, and such, and got my numbers. Despite the numbers...
  3. matt_crouch

    Find the magnitude of the gravitational field

    Homework Statement Find the magnitude of the gravitational field a distance r from an infinitly long uniform thin rod whose mass per unit length is (lamda) Homework Equations The Attempt at a Solution Need some clarification really i know dgx=-Gdm/r2 r=r2-r1 lamda=m/L...
  4. A

    Parallel plate capacitor with dielectric in a gravitational field.

    Homework Statement A square parallel plate capacitor with vertical plates of area A and distance d, charged with a constant charge Q and is completely filled with a dielectric material the same dimension as the gap between the plates, with dielectric constant k and mass m. Assuming the...
  5. G

    Energy Density of the gravitational field

    Why is there no satisfactory way to define the energy density of a gravitational field? Why must we use global energy concepts? I'm currently reading proofs of the Positive Energy Theorem, but none of the references explains why this is so. Can anyone explain it or point me to a good reference?
  6. S

    Meaning of Gravitational Field Outside Uniform Sphere

    Homework Statement I found this statement from my book : For points outside a uniform sphere of mass M, the gravitational fields is the same as that of a point mass M at the center of the sphere. My question : what is the meaning of it? Homework Equations g=G\frac{M}{r^2} The...
  7. B

    The speed of gravitational field propagation

    I am working on some interesting topics which relate to the speed at which gravity propagates. My question is this: within the frameworks of special and general relativity (or any other widely accepted theory, for that matter), is it necessary for gravitons/gravity waves to propagate at...
  8. M

    Range of the gravitational field

    When a body is fired upward with escape V (i.e 11.2 km/s) then what will be the height when the body leaves the gravitational field? I found by using formula 2gh=Vf^2 - Vi^2 keeping vf= 0 and vi=11200m/s then I got h=6400km= radius of the earth. Is it range of the gravitational field?
  9. P

    The mixture of two gases in gravitational field

    Two ideal gases are mixed in the box of infinite height placed in constant gravitational field. There are n_1 moles of the first gase and n_2 moles of the second. Their molar mases are M_1 and M_2 respectively. Let's assume that the temperature is constant. What's the molar concentration as...
  10. W

    Gravitational Field Related Question

    A satellite is designed to orbit Earth at an altitude above its surface that will place it in a gravitational field with a strength of 4.5 N/kg. a) Calculate the distance above the surface of Earth at which the satellite must orbit. b) Assusming the orbit is circular, calculate the...
  11. S

    How Strong is the Gravitational Field on a Neutron Star's Surface?

    Homework Statement What is the magnitude of the gravitational field at the surface of a neutron star whose mass is 1.80 times the mass of the Sun and whose radius is 9.3 km? Homework Equations g = GM/r2 The Attempt at a Solution G is ofcourse 6.67x10^-11 r^2 is 8.649x10^7 m...
  12. K

    Gravitational Field & Reference Frames

    In Newtonian physics gravity is a force and in relativity it's curved spacetime if I understand it correctly. So my question is, does the gravitational field of an object look different to different observers? What I mean is, does one reference frame see the strength of the field to be greater...
  13. C

    Object with no velocity is placed in a gravitational field

    My question is, if an object with no velocity is placed in a gravitational field, what causes it to accelerate? In Newton's theory of gravity, it was just accepted that if there is a force on an object, it accelerates. However, in general relativity, acceleration is now due to an object's...
  14. D

    Calculating Gravitational Field Constants for Mars, Jupiter, and Mercury

    1. Calculate the gravitational field constants for the following: Mars (r=3.43 x 10^6m , m= 6.37 x 10^23 kg) Jupiter (r= 7.18 x 10^7 , m = 1.90 x 10^27kg) Mercury (r=2.57 x 10^6m , m= 3.28 x 10^23 kg) 2. F = mg Fg = Gm1m2 r^2 3. So i tried subbing these given masses into the second...
  15. W

    Gravitational field intensity (help)

    I have this assignment in physics class and I'm stuck on this 1 question. What we were doing: We were hanging 0.10kg, 0.20kg weights etc.. on a Newton scale and we were recording the force of gravity. For 0.10kg I recorded 1 N, 0.20kg was 2 N, and so on until 1kg was 10 N. So the question...
  16. H

    Spring Harmonic Oscilation in Gravitational Field

    1. A mass M is attached to a fixed spring of constant K and oscillating with an amplitude A, the spring is hung from the ceiling in a gravitational field with constant free-fall acceleration g. 2. What is the oscillation frequency? Is it affected by gravity? Mx''=-Kx-mg => ?? 3. I figured it...
  17. A

    Redshift of Sound in a Gravitational Field

    Hi, Do sound waves experience a redshift similar to that of light in a gravitational field? Does anyone know the equation governing the change in frequency of the sound? Is this the same as the Doppler shift for an accelerating source of sound? Thanks.
  18. A

    Droplet's motion in electric field and gravitational field?

    Hello. A drop falling in air moves with terminal velocity (uniform velocity) when drag force balances its weight. But when charged droplet moves in electric field (In Millikan's Oil drop Method when there is vaccume between two plates) it is suspended between two plates when electric force...
  19. B

    Does the gravitational field have energy like the electric field ?

    We know that the energy density of the electric field is: \frac{1}{2}*\epsilon*E2 then, can we infer that the energy density of the gravitational field is: 1/(8\piG)*g2? Here, g is the gravitational field intensity
  20. R

    Escape Velocity and planet’s gravitational field

    Homework Statement The escape velocity is the velocity of an object at the surface of a planet that would allow it to be removed completely from the planet’s gravitational field. Calculate the escape velocity for an object on the surface of Pluto. mass of Pluto: 1.3 *1022 radius of...
  21. W

    Time dilation in gravitational field

    Homework Statement I recently had a test in the theory of relativity, and there was one task which I could not solve. This one has bothered me since the day I had the test. It was a compound task about GPS-satellites. There is no tricky calculations, or anything like that. The task aims at...
  22. F

    Can the gravitational field create its own gravity?

    We know matter/energy creates a gravitational field. But energy can be carried away from a system of orbitting bodies in the form of gravitational waves. So if gravitational fields can carry away energy (gravitational wave), then the gravitational field has an energy density in and of itself...
  23. B

    Solving Homework Problems: Electric Field & Gravitational Field

    Homework Statement Problem 1. A block having mass m and charge +Q is connected to an insulating spring having force constant k. The block lies on a frictionless, insulating horizontal track, and the system is immersed in a uniform electric field of magnitude E directed as shown in Figure...
  24. L

    Change in gravitational field strength

    Homework Statement The tallest spot on Earth is Mt. Everest. But another well-known mountain is the Mont Blanc, European Alps, which is 4807 m above sea level. If the radius of the Earth to sea level is 6367 km, how much does the gravitational field strength change between the sea level value...
  25. F

    Space-Time gravitational field problem

    Space-Time is deformed from a uniform gravitation field to one that is compressed inward so as to form a curvature. That curvature is uniform and can be understood as a series of decreasing diameters of circular field lines. If that is the case, then why are the planet's orbits elliptical and...
  26. G

    Energy of a particel in a gravitational field

    4. A particle is launched vertically from the surface of the earth, and rises to a height of 2RE above the surface before falling back. Ignore air resistance entirely. a) Find the initial speed of the particle. (Look up the necessary numbers.) b) This is a problem of motion in one dimension...
  27. K

    Big Bang - Gravitational field of antimatter + matter before annihilation

    I posted this question in the general physics section and the physics part has been answered somewhat. However the cosmological components remain un-answered. Would someone be kind enough to comment on those aspects please? Here is the question; Matter and Antimatter, I have always...
  28. G

    Rocket Acceleration in a Uniform Gravitational Field: Analyzing Momentum Change

    A rocket is accelerating upwards from rest in a uniform gravitational field g. Notation: m(t) is the mass of the rocket plus remaining fuel, m0 is the initial total mass, vex is the exhaust speed (relative to the rocket), and k is the rate, in kg/s, at which fuel is consumed. By considering...
  29. matt_crouch

    Gravitational Field Strength Calculations with a Pendulum

    As a pendulum can be used to calculate the gravitational field strength by using the equation Time period= 2(pi) sqrt (length/g) this equation assumes that the pendulum bob is moving in Simple harmonic motion. However at very small lengths the pendulum bob tends to move in a more...
  30. F

    Time for freefall in a varying gravitational field?

    I have been trying to calculate the time it takes for an object of negligible mass to free fall towards an object with a large mass, taking into account that the gravitational acceleration experienced by the small object increases as it moves closer to the big object. The first thing I tried...
  31. C

    Does a gravitational field have any effect on mass?

    Did General Relativity predict any mass changes of objects in a strong gravitational field?
  32. A

    How Do You Calculate the Gravitational Field Strength on Mars?

    Homework Statement A 250-kg space probe weighs 935 N on the surface of Mars. What is the gravitational field strength on the surface of Mars? Homework Equations W=mg g=Gm1/r^2 Fg=Gm1m2/r^2 The Attempt at a Solution Okay, so at first I thought it would be...
  33. D

    2-slit interference in a gravitational field

    Lets say I make 2-slit interf. experiment with slow (low enegry) electrons. I make their path as long as possible so they have time to fall in the Earth's gravitational field while they are flying. So electrons are attracted to the Earth, hence the Earth is attracted to the electron beam...
  34. F

    Gravitational Field Strength of Space Station w/ N Astronauts

    Homework Statement A space station consists of two living modules attached to a central hub on opposite sides of the hub by long corridors of equal length. Each living module contains N astronauts of equal mass. The mass of the space station is negligible compared to the mass of the astronauts...
  35. Math Jeans

    Particle in gravitational field

    Homework Statement Consider a particle of mass m constrained to move on the surface of a paraboloid whose equation (in cylindrical coordinates) is r^2=4az. If the particle is subject to a gravitational force, show that the frequency of small oscillations about a circular orbit with radius...
  36. J

    Gravitational Field problem Question

    Homework Statement Three objects -- two of mass m and one of mass M -- are located at three corners of a square of edge length l. Find the gravitational field g at the fourth corner due to these objects. (Express your answers in terms of the edge length l, the masses m and M, and the...
  37. W

    Question: Spin particles in scalar gravitational field

    The action of non-spinning particles in scalar gravity is S=-\int{\sqrt{-g}(\frac{1}{8\pi}g^{\mu\nu}\Phi_{,\mu}\Phi_{,\nu}-\rho e^{\Phi})d^4x} where \rho presents the comoving density. Now, I want to know the formula when particles with classical spin. Thank you!
  38. S

    Gravitational field for 2 particles

    Homework Statement Two identical particles, each of mass m, are located on the x-axis at x = +x0 and x = -x0. Determine a formula for the gravitational field due to these two particles for points on the y axis; that is, write \vec{g} as a function of y, m, x0, and so on. Express your...
  39. S

    Gravitational Field Strength Help

    Hello Everyone, I've been trying to get the answer to this problem for ages now and I just can't match my answer with the one in the back of the textbook. I hope you can let me know what I'm doing wrong. Homework Statement What is the gravitational field strength at a place 220 km above...
  40. D

    Earth's gravitational field strength

    Homework Statement (a) Find the altitude above the Earth's surface where Earth's gravitational field strength would be two-thirds of its value at the surface. Assume re = 6.371 multiplied by 10^3 km. wrong check mark km (b) Find the altitude above the Earth's surface where Earth's gravitational...
  41. G

    What is the gravitational Field?

    Hint: Use shell theorem and/or flux argument for a symmetrical shell. A thin spherical shell has a radius of 3.4 m and a mass of 456 kg. The Universal gravitational constant is 6.6726 x 10^-11 N m^2/kg^2. What is the gravitational field 1.4 m from the center of the shell? Answers in units of...
  42. A

    Limit to a gravitational field?

    If two objects, let's say two pool balls (or giant balls of neutronium for that matter), are placed in a closed universe that contains no other matter or energy, at rest with one another, is there a distance at which they exert absolutely no gravitational pull on each other? Or will there be...
  43. B

    Is holding something in a gravitational field doing work ?

    Is holding something in a gravitational field "doing work"? My son and I are on opposite sides of this question - if I am holding something in my hand in a gravitational field, am I doing work? My position is this - if I constantly accelerate a ball in space I am doing work. Since...
  44. snoopies622

    Exploring Metric of Uniform Gravitational Field: Is ds^2 Expression Correct?

    I just came across this expression ds^2 = (1+gz/c^2)^2(cdt)^2 - dx^2 - dy^2 - dz^2 in entry #19 of this thread [PLAIN] https://www.physicsforums.com/showthread.php?t=227753[/URL] for the metric of a uniform gravitational field. Is this correct? I was wondering because it yields...
  45. S

    Weightlessness due to gravitational field

    Astronauts in a space capsule orbiting the Earth at a height of 900km experience weightlessness: hence the gravitational field due to the Earth must be zero at that altitude'. Can someone please help ? What does it mean?
  46. S

    Electric field and gravitational field question

    Homework Statement making the worst possible combination of errors, an oxygen atom has a charge of 3.8x10^-39C. Treating the atoms as point particles, compare eletric force of two such oxygen atoms with gravitational force between atoms. is the net force repulsive or attractive...
  47. A

    Empirical evidence for gravitational field of EM radiation

    Hello, Is there any empirical evidence that electromagnetic radiation produces gravitational fields? I understand that as a form of energy it is expected to induce a spacetime curvature, but has this prediction of GR actually been tested? Is it at all subject to any controversy? Thanks, Armin
  48. L

    Gravitational field, density and mass.

    A satellite orbits a planet. The gravitational field strength at the radius of the orbit is 12 N/kg. What will the gravitational field strength at the position of the satellite be if - The planet's density is doubled? - The satellite's mass is doubled? I just don't understand their...
  49. A

    Similarity beetwen magnetic and gravitational field

    Hello everybody! I was read in a web page that magnetic field act over the ferromagnetic objects in the same way gravitational field act over any material object, mean magnetic field is a potential field energy as gravitational field. (http://van.physics.uiuc.edu/qa/listing.php?id=432") As...
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