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

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Doesn't some of Earth's gravity pull you sideways? Why doesn't this throw off calculations? [duplicate]

So, there's the gravity formula we all know, Fg=(Gm1m2)/r2. But not all of Earth's mass is directly below you, much of it is actually pulling you sideways. Yet, when doing calculations, the formula ...
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1answer
70 views

How do individual masses 'add up' to create a gravitational field?

The combined mass of the Earth is responsible for its local gravitational force. However, this combined mass is made up from of lots and lots (and lots) of atoms, each with their own individual mass ...
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3answers
81 views

Gravity effects when deleting stars or planets

In one of the latest SCIFI movies, they collect a star absorving it entirely in a kind of planet size gun/machine. As mass cannot disappear, I assume it was just concentrated inside their machine ...
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0answers
117 views

Nine Planets in the Solar System?

I just discovered that there is a Caltech team1 that suggests that there is "Evidence of a Ninth Planet": The object, which the researchers have nicknamed Planet Nine, has a mass about $10$ times ...
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3answers
130 views

Why is the gravitational multipole expansion taken with the origin at the centre of mass instead of the centre of gravity?

Wikipedia's article on the multipole expansion of the gravitational potential expands it as $$ V(\mathbf{x}) = - \frac{GM}{|\mathbf{x}|} - \frac{G}{|\mathbf{x}|} \int ...
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1answer
170 views

Why is the Taylor expansion of the gravitational potential cut off after first term?

In this answer to a question on this site, the gravitational potential of the Earth is expanded as $$U(r) \approx U(r_0) + \left.\frac {dU(r)}{dr}\right|_{r=r_0}(r-r_0),$$ keeping only the linear ...
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1answer
108 views

Relation between eccentric and true anomalies

If $v$ is the true anomaly and $E$ the eccentric anomaly, how can I show that $$\frac{dv}{dE}=\frac{b}{r}=\frac{\sin v}{\sin E}~?$$
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1answer
36 views

Tunnel through center of the earth, how to find period using $ adx=vdv$?

Suppose the boulder enters a tunnel dug through the center of the Earth along a diameter starting at rest. How would one calculate the time it takes for the boulder to reach the other end of the ...
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1answer
62 views

What powers a comet? [closed]

I know that a comet is a ball of ice, and I have tried the NASA page. http://spaceplace.nasa.gov/dr-marc-solar-system/en/#/review/dr-marc-solar-system/comet-power.html but they swerve around the ...
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1answer
62 views

Effect of air resistance on maximum height of thrown stone

Suppose a stone is thrown upwards from the surface of the Earth in a (very large) vacuum chamber and reaches a maximum height of 1km. If the same stone is thrown upwards at the same velocity outside ...
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1answer
63 views

Why do the stars in a binary system, revolve diametrically opposite to each other?

I encountered this question, as I was reading up on Gravity. The author of my textbook says that the stars orbit a common centre which is their center of mass. I somehow think that this fact might ...
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Does gravity turn itself off when it has nothing to work with?

The formula tells us that the force of gravity is equal to the mass of Object 1 multiplied by the mass of Object 2 multiplied by the Gravitational Constant and then divided by the distance between the ...
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1answer
37 views

How to model terminal velocity as a function of gravitational acceleration?

Taking the most simplistic form of terminal velocity, $v=\sqrt{\frac{mg}{c}}$ I want to try and derive an equation that models the velocity as g changes in height.. Because obviously the terminal ...
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1answer
104 views

Does Mass affect Speed of a Sliding Object With friction

Sorry if this has been already asked, but I've been looking around google for a while and couldn't find an answer suitable. I'm a beginning physics student so pardon the dumb question. Let's say we ...
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2answers
68 views

What size particle would be attracted to this 340 ton sculpture's gravitational field?

I know that gravity is a weak force, but this rock has mass, so it has gravity. The Levitated Mass sculpture is big enough to attract something. What is the largest particle that would "stick" to the ...
1
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1answer
54 views

Can a planet's orbit around a star be simulated? [closed]

Say I know all parameters like density, size, rotational velocity of a planet, could I predict its orbit around a star where I also know parameters of it? I want to design a simple model of the solar ...
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3answers
98 views

How to predict the location of a planet at a given time? [closed]

I am trying to create a simple two-dimensional computer simulation of a planetary system. While I've been able to understand Kepler's Laws of Planetary Motion, I do not know enough about the formulas ...
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0answers
42 views

What is the direction of the planet if we launch a rocket from it? [closed]

If we launch a rocket from a rest planet, then what is the direction of the planet after the rocket is launched ?I guess there are 2 possible answers: Move opposite the rocket because the planet is ...
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2answers
59 views

Are parts of objects part of that object's mass?

Disclosure: I'm not a physicist or a scientist, so there is a chance that this will seem like a silly question for some of you. But I'm really curious about this and I want to know the answer. ...
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31 views

What happens when something travels trough the center of gravity of something big? [duplicate]

For example, in a hypothetical case, imagine an object travelling through the center of the Earth. What happens in this case?
3
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1answer
73 views

Limitations of 2D point-mass Dynamics of the solar system

To model the solar system, I took the planets to be point masses, used newtonian mechanics and modelled the orbits as circular (only Mercury's orbit has appreciable eccentricity). The entire system is ...
3
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2answers
63 views

Would there be a “freefall zone” in the centre of a centrifugal artificial gravity?

In the novel Schismatrix, Bruce Sterling writes about people living on the inside of rotating cylinders (similar to Larry Niven's Ringworld and Iain M. Banks' Orbitals, but the atmosphere extends ...
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2answers
67 views

Can we decrease the value of $g$ (gravitational pull) without gaining height? [closed]

The value of $g$ on earth surface is $9.8\ \text{m/s}^2$ and when we gain height, then the value of $g$ decreases. Pilots experience same phenomena in air, but can we decrease the value of $g$ by ...
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0answers
60 views

Proof of the Gauss's law for gravity without divergence [duplicate]

The proof of the Gauss's law for gravity provided by Wikipedia takes use of the divergence theorem. Is it possible to arrive at the integral form of the Gauss's law in a way which doesn't require ...
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1answer
60 views

Gravitational Potential Energy misunderstandings [closed]

I'm really confused by the derivation of Gravitational Potiential Energy. I took a screenshot of the wikipedia entry below. My major confusion lies in: 1. The use of the position vector r in the ...
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3answers
70 views

How is Earth orbit possible? [duplicate]

What force other than gravity acts on objects in Earth orbit? Without such force, continued orbit would be impossible, as the object would be drawn to the Earth.
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29 views

Derivation Poisson's gravity equation by divergence theorem

I'm trying deduce the poisson's equation $\nabla^2\Phi (x)=-4\pi G\sigma(x)$ by divergence theorem Let $D:x^2+y^2+z^2\leq 1$ and $\sigma:D\to \mathbb{R}$ be the mass density function of $D$ (suppose ...
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0answers
68 views

Gravitational field due to inner shell on the outer shell [closed]

There're two uniform hollow shells of radius $R$ and $2R$ each. The one with radius $R$ is inside the larger shell touching the larger shell's inner surface and its center. What's the net ...
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1answer
51 views

Gravitational potential of planets

How do you work out the gravitational potential of planets in the solar system? Do orbiting planets have gpe? And what would it be relative to? The equation I know for it is mgh. But what would the ...
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2answers
109 views

Orbital mechanics: will a satellite crash?

For a satellite given an initial speed and position above a planet, I'd like to know whether it will experience an elliptical, circular, parabolic or hyperbolic trajectory, or crash into the planet. ...
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1answer
86 views

Why do the satellites revolves on a circular path around a planet at orbital velocity? [duplicate]

We know that there is a particular velocity with which a satellite will move in a circular orbit ( orbital velocity ) but if its velocity is more than the orbital velocity but less than the escape ...
2
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1answer
59 views

The source of work by gravity force [duplicate]

I learn that any work needs a source of energy, the work of gravity force (like keeping the Moon in the orbit by the Earth gravity force) comes from where? Can we find any mass reduction (transform ...
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21 views

The amount of force needed to bend and break a magnesium cylinder? [closed]

I want to determine how much force in Newtons will be need to bend a solid cylinder of magnesium. The cylinder is (x) cm in diameter, and it is (l) cm long. The density of normal magnesium alloy is ...
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0answers
40 views

Free Falling Bodies [closed]

An object is thrown vertically upward. It has a speed of 10ft/s when it reached one-half its maximum height. since this is a thrown object it's initial velocity is a mystery, is it right to make ...
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0answers
21 views

Can you do an n-body simulation in terms of energy and momentum?

An N-body simulation typically works directly in terms of the gravitational forces and accelerations. If you can solve the equations exactly, this is fine, but there are many instances where this is ...
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1answer
31 views

Falling objects with different masses

I know that free falling objects with different masses fall at the same rate but that does not explain why objects with big masses are heavier to lift? what is gravity anyway I know it isn't a force ...
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5answers
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Why do objects in a gravity simulation experience sudden large accelerations?

I'm trying to create a simple program that simulates gravity. The idea is that I have one central sun and several planets that I can create with a swipe gesture on the screen, and I use the initial ...
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7answers
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If I toss a coin, vertically, on the surface of Mars, will it land back in my hand?

When I toss a coin in Mars, is the planets atmosphere rare enough that I'd rotate with the planet (at its angular velocity), but not the coin?
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2answers
55 views

How is the equation for force by charge or by mass discovered?

It's a newbie question. How is the formula for force between two charges or gravitational force between two particles derived. Is it just intuition or is there any method used to derive these ...
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2answers
70 views

What would happen if the gravitational force was repulsive? [closed]

Since my young age, I have always been somewhat afraid of looking up at the sky for one weird reason. It always made me think about this irrational deep dark fear that I have: What if we stopped ...
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1answer
49 views

Lollipop 3d choreography animation

I initially wanted to recreate the little dancing dots android lollipop's boot animation in javascript: For that, I've implemented a 3d $n$-body simulation (with css and js): ...
2
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1answer
57 views

How much microgravity is there on ISS due to tidal forces? [closed]

I used the equation for the tidal force: $$ F = \frac{2GMd}{r^3} $$ where $M$ is the mass of the Earth ($5.972 \times 10^{24}$ kg), $d$ is half the length of ISS ($50$ m), $r$ distance from center ...
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2answers
48 views

Question about Cavendish experiment

I got a question. In Cavendish experiment was used lead in both of spheres. Can we repeat that experiment with balls made from stone or anything else. Because lead could be a byproduct of radioactive ...
3
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0answers
56 views

How can escape velocity be independent of the direction of projection of a body?

I read that the escape velocity of a body is independent of the direction of projection. For example, I could throw a ball at $11.2$ km/s velocity horizontally, and it would still leave earth. I am ...
3
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1answer
58 views

Effective mass of two objects

I read that if we want to perform conservation of energy taking one object as frame of reference, we need to assume that the other object has the effective mass and velocity. And effective mass is ...
2
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3answers
39 views

What is the gravitational pull if one has as much mass above them as below them? [duplicate]

I understand the previous responses to other answering if you were at the center of a planet, would you be weightless? Yes you would due to the forces of gravity pulling at you from all sides. ...
2
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2answers
44 views

The way planets rotate and revolve [duplicate]

Why is that the all planets move in the same plane?(correct me if I'm wrong) Why not some of them in anticlockwise direction and others in clockwise direction?
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1answer
58 views

Angular Momentum and Kepler's Second Law

Let me preface by saying that I get the gist of the conservation of angular momentum, at least qualitatively. To better illustrate my question, I will consider the case of a planet orbiting a star. ...
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1answer
46 views

Gravitational field within a solid sphere with a hole on it [closed]

I want to calculate the gravitational field at $p'$, we know that the sphere has a uniform density $\rho$. Basically what I tried to do to solve this problem was to calculate the potential exerted by ...
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1answer
50 views

How long would a non-gravitationally assisted flight take to Pluto?

Say you want to fly to Pluto from Earth and orbit it. So you're going to launch it from Earth with such a speed that as it approaches Pluto, it's traveling (roughly) the same linear speed of Pluto. ...