# Tagged Questions

The Newtonian model of gravity in which the force between two objects is given by GMm/r^2.

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Why is graviton not found yet? Newton said gravity pulls us, Einstein said space is bent and it pushes us, hawking predicts the existence of graviton and 'hawking radiation'. How far are we from ...
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### Why do constants have dimensions?

I am just a beginner in dimensional analysis, and I see that $G$, the universal gravitational constant, is independent of everything. Speed, for example, depends on distance and time, but $G$ does not ...
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### Question related to accleration due to gravity [closed]

What effect will be seen on the value of accleration due to gravity if radius of the earth is decreased keeping the mass constant?
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### Orbiting in space (free fall) and centripetal force?

So basically astronauts are weightless b/c they are free falling. But to get to that state they need to be moving real fast. So why doesn't that speed along with the centripetal force affect them? I ...
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### Stars more affected by gravity of stars further away, need help understanding argument why

In the first chapter of Binney and Tremaine's "Galactic Dynamics" there is a statement that I don't yet understand. The first chapter of the book is linked here, straight from the publisher. The ...
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### Acceleration due to conservation of angular momentum in absence of a force

I don't understand why the conservation of angular momentum can imply an acceleration, in absence of a force. Consider for istance planetary motion. The angular momentum $\vec{L}$ of the planets is ...
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### Difference between gravity and standing on a platform accelerating upwards at 9.81 m/s^2

So, according to Einstein's theory of general relativity, gravity is not a force instead it is a consequence of objects with mass deforming spacetime, right? And so, according to him, there is no ...
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### Why does mechanical energy have to equal zero to find escape velocity?

A object orbiting the earth has total mechanical energy equal to \begin{align*} E^{mech} = \frac{1}{2} m v^2 - \frac{GMm}{r} \end{align*} with $M$ the mass of the earth and $r$ the distance. My course ...
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### Sphere through Torus

In the following picture (it's awful) , What would happen if the sphere and the torus (the sphere can pass through the hole of the torus) are left in an empty space ? I assume (I am probably wrong) ...
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### Can a satellite be put into orbit such that it will always remain directly over a city? [duplicate]

Isn't it possible if we just set it high enough so that it's angular speed matches with the earth's? I think that the city must be on the equator to make this happen. Am I correct? Please can anyone ...
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### Can a body under weightlessness detect if it's under free fall or under a zero gravity field?

My first thought was to use an accelerometer. However, quoting from wikipedia, an accelerometer at rest on the surface of the Earth will measure an acceleration g= 9.81 m/s2 straight upwards. By ...
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### Show that Newtonian orbits are closed and periodic

I want to prove to show that the change of the rotation angle of a body in a two-body-problem is exactly $\Delta \phi = 2\pi$. I know that the whole energy of the system is given by  E = \left(\...
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### Newton's law of gravitational attraction [closed]

My teacher would like us to use Newton's law of gravitational attraction to solve a question similar to this one: "Two objects exert a force of gravity of 20N. One object's mass is increased by a ...
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### Can you lift heavy objects in zero gravity? [closed]

I'm not someone who majored in physics and i never took the subject seriously when i was in school and im regretting that alot, there's so many things going in my mind that i cannot answer because i ...
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### What is difference between 9.8 N (Kgwt) and 9.8 m/s^2 (g)?

What is difference between 9.8 N (Kgwt) and 9.8 m/s^2 (g)? What is difference between kg weight and gravity? I am not so good in physics so please explain in a lot of detail (but sorry for this silly ...
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### How does Newtonian gravitation conflict with special relativity?

In the Wikipedia article Classical Field Theory (Gravitation), it says After Newtonian gravitation was found to be inconsistent with special relativity, . . . I don't see how Newtonian ...
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### Why do objects with mass have gravitational force that is proportional to their mass?

Why do objects with mass have gravitational force that is proportional to their mass, i.e the larger the object the more gravitational force it has?
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### Books on Celestial Mechanics [duplicate]

My background is mathematics. I would like to study celestial (not classical) mechanics and looking for an appropriate book. I found that somebody has already asked a similar question "How to learn ...
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### Binding energy of a galaxy?

I'm a novice in physics and new to the forms, so please forgive me if this is a dumb question or if this is in the wrong section to be posted, but how would one find the gravitational binding energy ...
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### Can low-gravity planets sustain a breathable atmosphere?

If astronauts could deliver a large quantity of breathable air to somewhere with lower gravity, such as Earth's moon, would the air form an atmosphere, or would it float away and disappear? Is there a ...
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### Relations between Maxwell-Boltzmann's distribution and the n-body problem velocities distribution

Solving the n-body problem numerically and finding the velocities distribution, one finds that it's quite similar to Maxwell-Boltzmann's velocity distribution. This is quite suprising because of the ...
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### How to visualize gravity fields? [closed]

I'm creating a tool for intuitively prototyping routes through space. Part of this requires visualizing gravity. This is the formula for working at how much gravity is at a particular location: <...
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### Force of Gravity of a stationary object acting on another object moving through space

Story: I have x and y positions of a spaceship as it moves through space to some goal location at [1000, 700]. A record of its movement is given by: ...
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### Explanation of a Mechanical Situation [closed]

The box sitting on the table top has some mass $m$ (I would refer to the weight of the box just as $\mathbf{W}$), and its net acceleration which I call $\mathbf{a}$ is zero, for the time being. This ...
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### Solving the two body problem numerically

I'm trying to solve the two body problem numerically, setting up $G$, $m1$ and $m2$ to be equal to 1. then I located each mass on positions -5 and 5 respectively along the $x$ axis and gave them both ...
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### Newtonian Gravity Simulator?

Could anyone suggest me a good (and possibly free) Newtonian Gravity Simulator software available on the web, where it might be possible to simulate the Solar System dynamics and playing with it, by ...
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### If two objects have the same drag coefficient, but one is much heavier, would it fall faster?

Not sure this is a good example but imagine we have two feathers, both with exactly the same drag coefficient, they have the exact same shape and everything, but the only difference is that one of ...
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### Apparent non-aberration of gravitational waves

Since GR assumes that gravitational waves travel at speed $c$, we expect we would be able to some day detect an aberration effect similar the that of light. Of course, gravitational waves are so tiny ...
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### Pendulum at an angle

A pendulum has a period of $T$ when swinging from a string. The pendulum is now placed on a frictionless incline at a 30 degree angle. What is the new period of the pendulum?
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### What effect does the Moon and Sun have on gravity? [duplicate]

I know that every object has a gravitational pull regardless of how far or how small it is. It's just that generally this force is negligible. Does the force produced by the sun and moon have any non-...
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### Do animals defy gravity? [closed]

I am a beginner and trying to understand the concept of gravity Do animals defy gravity? If yes, which animal defies and in what way it does? Sorry had I asked something wrong
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### Distance from Earth where gravity becomes negligible

This is a basic little problem I thought up when trying to remember some physics, and I wanted to see if it's at all correct: trying to figure out the distance from earth where gravity becomes ...
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### Gravity Vs Distance [closed]

What is the relationship between the magnitude of Earth's gravity and the distance away from the Earth's surface? Or at what rate does gravity decrease as one moves away from Earth?
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### What would happen to the orbital radius of the Earth if the radius of the Sun is decreased but without any loss of its mass?

What would happen to the orbital radius of the Earth if the radius of the Sun is decreased but without any loss of its mass? According to Newtonian gravity the acceleration due to gravity will ...
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### Satellite and gravitational acceleration

According to $0.5gt^2$ object will fall 5m in first second. Earth curve is 5m for 8km So if we can project object at 8000 m/s speed object will never fall into ground. Above scenario is correct ...
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### What is the Role of gravity?

I am new to physics and I understand gravity is a pulling force. Let's assume a ball has been placed on the ground. Does gravity has any role after I placed an object (e.g. ball) on ground? Sorry,...
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### Classical gravitational waves, again [duplicate]

I'm basically duplicating this question, because I'm not satisfied with the answer. Here's why I'm not satisfied. If we know that "gravity travels at a finite speed", then it seems obvious that it ...
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### What Keeps a Pendulum Moving In a Circular Path?

From the figure, we know that $F_{net} = mg\sin\theta$. Now, this force $\vec{F_{net}}$ is in the direction of the velocity $\vec{v}$ of the bob, both are tangent to the path. Therefore, the net ...
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### Can the constant $k$ from Kepler's third law be independent of the mass of the planet?

Consider Kepler's third law The square of the orbital period $\tau$ of a planet is directly proportional to the cube of the semi-major axis of its orbit $a$. $\frac{\tau^2}{a^3}=k$ The ...