# Gravitational field Definition and 15 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. ### A Does a linearly accelerated observer inside an inertial spherical charged shell detect an electric field?

The electric field inside a charged spherical shell moving inertially is, per Gauss's law, zero. If the spherical shell is accelerated, the field inside is not zero anymore, but it gains a non-null component along the direction of the acceleration, as mentioned, for example, in this paper. The...
2. ### B A question from Resnik about g-force

Suppose there is one force gravitational force ##\vec{f_g}##. We can relate this downward force and downward acceleration with Newton sec law. This law can be written as ##F_{net,y}=ma_y## which becomes $$-F_g=m(-g)$$ or $$F_g=mg$$ $$\vec{F_g}=-F_g \hat j=-mg \hat j=m\vec g$$. Is it right...
3. ### I Problem with gravitation field perpendicular vector.

since it is known that ##\vec{A_\perp} = -{mG \over R^2}## why did the professor write it as ##\vec{A_\perp} = {- R G \rho \over 3}## for perfect sphere with perfect mass distribution ? Shouldn't it be ##\vec{A_\perp} = -{4 \over 3} \pi R G \rho##? I need help thanks.
4. ### Electrons orbiting the Earth

I've been given a question to find the magnetic flux density of the Earth if an electron is orbiting near to the surface. The answer to the question makes the magnetic force equal to the centripetal force and solves for B from there. However, I am confused to why the gravitational force has no...
5. S

### Derivation of an expression for centripetal acceleration

Homework Statement I have derived the expression for the velocity of the satellite v= root of GM/r however I'm struggling to derive an expression for the centripetal acceleration of a satellite orbiting Earth. Homework Equations The Attempt at a Solution I'm not entirely sure which equations...
6. ### Finding where the gravitational field strength is 0

1. Homework Statement Homework Equations g = (Gm)/r2 The Attempt at a Solution I tried doing (Gm1)/a2 = (Gm2)/(r-a)2 where a is equal to the distance from the position we're trying to find to the center of the most massive object but end up getting a quadratic in the denominator on the right...
7. ### Relativity Looking for a good book on GR

Hello, I would like to better understand the geometric evolution of a gravitational field of a simple point mass as the velocity difference between two different inertial frames approaches the speed of light. I would also then like to extend into more complex scenarios such as charged...
8. ### Falling object in a gravitational field with v^2 drag force

Homework Statement Consider a particle in a gravitational field that is also subject to a resisting force proportional to the velocity squared ( Fdrag = + or - cv2). a) Find the terminal velocity, vT, for the object as it falls. b) Show that for an object dropped from rest that the velocity...
9. ### I Time in gravitational reference frame?

Hi, so Newton said that gravity was like or equivalent to a force? When I learned about SR we were talking about the passing of time as defined by a photon bouncing between two parallel mirrors. So when we're sitting our two parallel mirrors in a gravitational field, even though I suppose...
10. ### Difference between spacetime and the gravitational field?

Are spacetime and the gravitational quantum field (still hypothetical) separate entities? Would the gravitational field be more fundamental, one of the various entities from which spacetime as a whole is composed? Gravitons, which are believed to transmit the force of gravity, would surely be...
11. ### Gravitational field

Hey guys, take a look at this question if you may Suppose the moon, instead of a sphere, is a disc orbitating the Earth ( the moon's total mass is equal to the disc's total mass), the intern radius of the disc is equal to half the distnce between moon and Earth's center of mass and the external...
12. ### Gravitational Field and free fall

The acceleration of free fall at the equator is not equal to the acceleration of free fall at the poles.explain?
13. ### Gravitational Field Lines

Homework Statement "Complete the diagram to display gravitational field lines between two objects of equal mass." Homework Equations N/A as question is descriptive. The Attempt at a Solution Okay, I know it's a bit of a mess but what I'm trying to show here is that the fields are radial...
14. ### Line Integral Example - mistake or am I missing something?

This is an example at the beginning of the section on the Fundamental Theorem for Line Integrals. 1. Homework Statement Find the work done by the gravitational field \vec{F}(\vec{x}) = -\frac{mMG}{|\vec{x}|^3}\vec{x} in moving a particle from the point (3,4,12) to (2,2,0) along a piece wise...
15. ### Quantum anti-gravity?

Am I reading some more recent articles on quantum gravity correctly that seem to be implying that a coherent particle is not subject to gravity? If you have a coherent C70 buckyball molecule (see Zeilinger - Update: "Matter-wave interferometer for large molecules", Jan. 2002), the force of...