All Questions
Tagged with gravity newtonian-gravity
404
questions
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77
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How much time does it take for an object to fall from space? [closed]
Let's say there's an object of mass $m$ in space, $h$ meters away from the surface of the Earth. $h$ is large enough that $g$ cannot be assumed to be constant. The acceleration varies according to ...
- 117
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0
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31
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Better equations for modeling and simulating a halo orbit?
I'm trying to model a halo orbit at low altitude (10m from surface). The satellite is using propulsion to trace the circular halo path. It looks like this "from the top" (the blue ball is ...
- 231
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57
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When is it appropriate to say Newtonian gravity is a force? When is it not appropiate? [closed]
Please help me understand the notion of force when it is applied to Newtonian gravity. From my understanding forces in physics involve interactions with at least 2 objects and can cause an ...
- 431
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41
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Dual of Newtonian gravitational field
In the static state, the laws of Newtonian gravity and Coulomb force have exactly same formulas,
$$F = K \frac{A_1A_2}{r^2}.$$
In the electrical case, moving materials produce a field, say a dual ...
- 1,409
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42
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Einstein's equation of gravitation field [duplicate]
I'm looking for the reason why there is the number eight $8$ at the r.h.s. of EI:
$$R_{\mu\nu}-\frac{1}{2}Rg_{\mu\nu}=\frac{8\pi G}{c^2}T_{\mu\nu}.$$
My attempt was to take the limit of this equation ...
- 255
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52
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Gravitational potential due to arbitrary shape
Outside the uniform sphere, the potential is expressed as if all the masses are concentrated in the center of the sphere.
Is it also true for arbitrary shape?
That is, outside any body, is potential ...
- 51
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89
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How does gravity act and propagate in a 2+1D universe?—Newtonian versus general relativity
In a hypothetical 2+1D universe:
if we apply the Newtonian concept of gravity, we might expect that the gravitational force between two mass points with a distance of $r$ would diminish linearly with ...
- 618
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107
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References on Newton-Cartan Gravity
I'm interested in learning a bit about Newton-Cartan gravity, and I would like some references on the topic. I am already familiar with differential geometry and general relativity, so those could be ...
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2
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33
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Understanding conservation of angular momentum in relation with rotating objects
Conservation of angular momentum says that the angular momentum of a closed system will not change if there is no external torque applied to the system. For example, let's take the example of a ...
- 665
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139
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Physical relevance of the $ij$ components of the Einstein field equations in the Newtonian limit
In the weak field limit of general relativity (with matter described by a perfect fluid consisting only of dust), we have the following correspondences:
$00$-component of the Einstein field equations ...
- 830
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If most of an atom's mass comes from binding energy, why did people think that anti-hydrogen could fall up if antimatter had negative mass?
Antimatter isn't bound by anti-energy, so doesn't that mean that even if elementary antimatter particles had negative mass, the total mass of an anti-atom would still be overwhelmingly positive?
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Negative Energy and Gravity
Why do many science communicators say that negative masses fall upwards? Is it the same in the physics literature that they say that negative masses fall upwards?
In general relativity, things don't ...
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51
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Newtonian approximation for the tidal forces at the event horizon of a black hole
I'm currently working on a problem where I have to calculate the tidal forces a person experiences if their feet touches the Schwartzschild radius and their head is $1.8m$ elevated above the ...
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37
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Trying to understand Gravitational Field
I have learned that gravitational potential is defined as the amount of work done on bringing the mass from infinity to distance r.
But what does that infinity signify in the definition, I mean like ...
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2
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181
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How much kinetic energy would a star in a galaxy have if it fell to the center?
I want to calculate the speed, or equivalently, the kinetic energy of a star, if it had no rotational speed and fell from a given radius to the center of the galaxy.
I assume Newton's shell theorem ...
- 476
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29
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Describe the decrease in potential energy if two forces are acting on it one conservative which is greater than other applied by us in opposite dirn [closed]
So imagine this situation.
An object is experiencing two forces, one due to gravity in downward direction and other applied by us in upward direction such that our force is less than gravitational ...
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Contradiction in negative mass interactions according to GR
I quote Sabine Hossenfelder:
Gravitation is a spin-2 interaction. It is straightforward to see that this means that like charges attract and unlike charges repel. The charge of gravity is the mass. ...
- 476
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What is the difference between GPE and gravitational self energy in GR?
What is the difference between gravitational potential energy and gravitational self energy in General Relativity? Are they both the same in Newtonian gravity?
- 476
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39
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How a force that is always perpendicular to velocity can change the kinetic energy when another force is acting oppposite to velocity? [closed]
When a satellite is revolving around a planet with an orbital velocity in presence of air resistance, the satellite's Kinetic Energy keeps on increasing as it falls down. The resistive force is trying ...
- 101
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4
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525
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Interpretation of gravitational waves
A wave has peaks and valleys. I can think of a sine wave as a wave with peaks and valleys.
Now, if gravity is a wave, can we say that gravity would have peaks and valleys, with the valley becoming ...
- 1,023
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2
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190
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What is the gravitational field intensity of a uniformly distributed mass content in Newtonian gravity?
In an infinite universe composed of single point masses which can be simplified as a uniformly distributed mass density, what is the equation for the gravitational field intensity in Newtonian gravity?...
- 476
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267
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How to calculate the period of non-circular orbits?
How to calculate the period of non-circular orbits?
By conservation of mechanical energy:
$$
E = -\frac{GMm}{r} + \frac{1}{2}\mu \left ( \dot{r}^2 + r^2 \dot{\theta}^2 \right )
$$
By the conservation ...
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44
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How is when an object moves gravity not effect it ? As Einstein sais?
Experiment:
*a water bottle with a hole . Water is falling from the hole when the bottle is in rest . When the bottle is released and falls , water stops falling as gravity is not doing effect on it . ...
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118
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Is there an equation that is quick to use that calculates gravity around black holes?
Is there an equation the can calculate gravity around black holes but is less time consuming than EFE? I want to find an equation that is simpler/faster than Einstein's Field Equations but can still ...
2
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1
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55
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Does MOND respect linear superposition of gravitational field intensities?
Does Milgrom's MOND respect linear superposition of gravitational field intensities as Newtonian gravity does?
- 476
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2
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119
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Since when did inertial mass and gravitional mass became equal?
If we think about inertial mass and gravitational mass as independent concepts and develop physics then we would know after a while they are only propotional (by precision we have by now). but it seem ...
- 1,409
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139
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Star with quadrupole in binary system violates Newton's 3th law?
Suppose that, in a binary system of two stars, the star A (and only the star A) has a non-zero quadrupole moment $Q_A$. Then, the star B feels the usual gravity force plus an additional force, ...
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140
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Do objects with non-uniform shapes and mass distributions rotate as a result of gravitational attraction?
I was thinking about orbital mechanics this morning and a question arose: do objects with non-uniform shapes and mass distributions rotate as a result of gravitational attraction?
Thinking through the ...
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2
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695
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General relativity when can we approximate to Newtonian gravity?
Lets consider this scenario in deep void of space where other curvatures of large objects are negligible in this case and we bring 2 objects lets say $A$ and $B$.
We give it a force slightly lower ...
- 441
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84
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Newton's approximation of 2+1D gravity
I learnt that the curvature tensor in 2+1D spacetime is zero in vacuum. How is it possible to come from there to the Newton's theory in 2D + time, where I guess, the gravitational force law is still ...
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