The Newtonian model of gravity in which the force between two objects is given by GMm/r^2.
0
votes
1answer
106 views
How is gravitational force is compared to flow of water?
I listened to a lecture. The professor said that the gravitational field around the particle (spherical in shape) can be compared to a pond having a constant height and depth and water is constantly ...
2
votes
5answers
238 views
Einstein gravity versus Newton's gravity
What's the basic difference between the gravity as seen by Einstein, and that by Newton?
1
vote
2answers
99 views
Is quantum mechanics similar newtons laws of gravity? In a way [duplicate]
Is quantum mechanics similar to Newtonian gravity in respect that it explains how something works but not why it works? Or does Quantum mechanics explain why it works? (I haven't actually studied QM)
...
2
votes
2answers
97 views
Where are we : On level ground or on a ramp - moving in a train?
Let's say we are traveling in a train. The path has two parts: one at ground-level and the other moving up on the ramp. The ramp has an inclination of $\arctan\frac{a}{g}$ with the horizontal, where ...
7
votes
1answer
125 views
Gravitationally bound systems in an expanding universe
This isn't yet a complete question; rather, I'm looking for a qual-level question and answer describing a gravitationally bound system in an expanding universe. Since it's qual level, this needs a ...
1
vote
0answers
61 views
Formulation of the Three-Body Newtonian problem
I am trying to understand three body problem in Newtonian space. I want to make formulation of differential equations for known initial conditions for the case with:
Identical three masses
...
2
votes
2answers
145 views
Infinitely many planets on a line, with Newtonian gravity
(I apologize if this question is too theoretical for this site.)
This is related to the answer here, although I came up with it independently of that. $\:$ Suppose we
have a unit mass planet at each ...
5
votes
1answer
113 views
Slinky base does not immediately fall due to gravity
Why does the base of this slinky not fall immediately to gravity. My guess is tension in the springs is a force > mass*gravity but even then it is dumbfounding.
0
votes
1answer
51 views
Weightlessness for astronauts
Well, this question has been puzzling me for kinda long time, many people believe that orbiting astronauts feel weightless because they are "beyond the pull of earth's gravity"...How far from the ...
2
votes
1answer
149 views
Newton's Law of Graviation: Why G?
I've been wondering, in Coulomb's Law, $k_e = \dfrac{1}{4\pi\epsilon_0}$. Therefore, why do we use $G$ in Newton's Law of Gravitation? What if the constant is more like Coulomb's Law, e.g.
$G = ...
1
vote
4answers
143 views
How to get the angle needed for a projectile to pass through a given point for trajectory plotting
I am trying to find the angle needed for a projectile to pass-through a given point.
Here is what I do know:
Starting Point $(x_0,y_0)$
Velocity
Pass-through point $(x_1, y_1)$
I also need to ...
2
votes
1answer
117 views
Newtonian Gravity on a Riemannian $3$-Manifold
To solve the Poisson equation for the Newton Potential, say $\phi$, one can use the divergence theorem, such that
$$\int_U \nabla^2 \phi \sqrt{g}~ dV= \int_{\partial U} <\nabla \phi,n> ...
3
votes
3answers
207 views
Gravitational Potential of a Sphere vs Gravitational Binding Energy of a Sphere
My question is about two equations regarding uniform spheres that I've run into:
$V=\frac{GM}{r}$
... and ...
$U = \frac{3}{5}\frac{GM^2}{r^2}$
$V$ is unknown to me, and is described (in Solved ...
1
vote
1answer
62 views
Distance traveled in a simple two body problem [duplicate]
I'm trying to program an $N$-body simulation and I'd like to be able to test it with a known solution to a simple, two-body problem. I've looked at multiple sources, but I just don't know how to apply ...
1
vote
3answers
243 views
Similarity between the Coulomb force and Newton's gravitational force
Coulomb force and gravitational force has the same governing equation. So they should be same in nature. A moving electric charge creates magnetic field, so a moving mass should create some force ...
2
votes
1answer
183 views
How can a satellite's speed decrease without its orbital angular momentum changing?
I have no idea what the answer is. I'm supposed to answer it within 3-4 sentences.
0
votes
3answers
85 views
Stresses in asteroid during close flyby
The acceleration of an asteroid (such as 2012DA14) as it approaches earth is proportional to the reciprocal of distance $r$ from earth center, squared. the derivative of the acceleration, or jerk, is ...
6
votes
4answers
326 views
What's the exact gravitational force between spherically symmetric masses?
Consider spherical symmetric$^1$ masses of radii $R_1$ and $R_2$, with spherical symmetric density distributions $\rho_1(r_1)$ and $\rho_2(r_2)$, and with a distance between the centers of the spheres ...
2
votes
2answers
81 views
Shoot object into the Sun using minimal energy
Say I want to shoot a cannonball into the Sun with minimal energy (minimal initial velocity relative to Earth).
In which direction do I shoot it?
Let's neglect Earth's gravity, if that would make ...
16
votes
4answers
588 views
Staying in orbit - but doesn't any perturbation start a positive feedback?
I am not a physicist; I am a software engineer. While trying to fall asleep recently, I started thinking about the following.
There are many explanations online of how any object stays in orbit. The ...
0
votes
2answers
81 views
How is space ship's acceleration perceived if the acceleration is perpendicular to the velocity?
Spacecraft in orbit around the Earth are constantly accelerated by the gravitational field of Earth. That's why the spacecraft ($m \ll M$) is in an (elliptical) orbit around the centre of gravity of ...
1
vote
2answers
86 views
Escape Velocity question
I would like some help in understanding the derivation of the formula for escape velocity.
Why does $t$ approach infinity? And why is $v(t)$ approaching zero?
I know that $r(t)$ is infinite because ...
1
vote
1answer
87 views
Weightlessness on Earth
Would the following work?
Imagine one would
1) create a straight 4000 km long tube (at ground level), following the curvature of the Earth, wide enough to hold a pod the size of an aircraft cabin;
...
6
votes
6answers
536 views
When driving uphill why can't I reach a velocity that I would have been able to maintain if I started with it?
Consider these two situations when driving on a long straight road uphill:
Starting at a high velocity $v_h$, which the car is able to maintain.
Starting at a lower velocity $v_l$, and then trying ...
1
vote
1answer
190 views
Gravity and free fall
In Wikipedia it's stated that "[..] gravity, is the natural phenomenon by which physical bodies appear to attract each other with a force proportional to their masses".
Then I found many examples ...
2
votes
3answers
186 views
If you could reverse gravity, what velocity would you achieve on leaving Earth?
If you could reverse gravity, to make it repulsive instead of attractive, what velocity would you achieve on leaving Earth? A simple question really, but I have completely forgot how to calculate ...
0
votes
1answer
84 views
Lagrange L4 L5 points and perifocal plane
I have 2 satellites at the L4 and L5 points and these are watching an object. Each satellite provides the angle to the object from its own position from a line parallel to the $\text{x-axis}$ of ...
0
votes
3answers
153 views
What was wrong with action a distance?
It is usually said that the idea of fields was introduced (electric and magnetic fields) in electricity and magnetism after Coulomb's law to cure the conceptual problems of action at a distance.
...
1
vote
1answer
99 views
The Value of Newton's Gravitational Constant $G$ within an Atom
Can the value of Newton's Gravitational Constant $G$ be measured within a stably bound atom?
PLEASE NOTE: Since scattering experiments do not involve stably bound systems, their results are not ...
3
votes
4answers
573 views
Why does an object thrown parallel to the ground eventually fall down?
Suppose an object is thrown parallel to the ground. The gravity acts downward (ie. perpendicular to the direction of motion of the object). The work done by gravity on that object will be given by :
...
0
votes
2answers
454 views
Newtonian gravity vs. general relativity: exactly how wrong is Newton?
Is there a simple function I can use to describe the difference between simple Newtonian dynamics and the actual observed motion? Or maybe some ratios for common examples of, say, the motion of stars ...
0
votes
1answer
169 views
Energy in orbit of satellites around the earth lost?
If the total mechanical energy in a satellite's orbit (assuming circular) is greater when it is closer to the earth, and hence smaller when it is farther from the earth, then we can say that as the ...
0
votes
1answer
148 views
Two moons of Earth?
Hypothetically, suppose there is a situation where the Earth's moon gets neatly sliced into two equal hemispheres, and the force responsible for this slicing also creates a distance between the two ...
1
vote
1answer
97 views
Idealized trajectory from sloped surface
I am a GIS programmer implementing a visualization.
I am modeling the idealized trajectory of a particle ejected from a volcanic vent using:
$$\text{distance} = \frac{(v^2 \times ...
0
votes
1answer
57 views
Gravity question [duplicate]
Possible Duplicate:
Don’t heavier objects actually fall faster because they exert their own gravity?
When true: The force pulling the "heavy" object down is greater BUT it also takes more ...
0
votes
6answers
202 views
Relation between field strength and potential?
In terms of gravity and electric fields, I'm not sure what the difference is between field strength and potential is and how they are related? Both using maths and not.
9
votes
3answers
457 views
Gravity in other dimensions than 3 and stable orbits
I have heard from here that stable orbits (ones that require a large amount of force to push it significantly out of it's elliptical path) can only exist in a three spatial dimensions because gravity ...
0
votes
1answer
156 views
If 2 charges have the same sign, the coulomb force is positive but repulsive, while with 2 masses the gravitational force is positive but attractive
If you have two point objects both the same positive charge and both of the same mass at a distance $r$ from each other.
The force between them due to gravity is $F_g=\frac{Gmm}{r^2}$ and $F_g$ is ...
3
votes
4answers
1k views
What is the difference between center of mass and center of gravity?
What is the difference between center of mass and center of gravity?
These terms seem to be used interchangeably.
Is there a difference between them for non-moving object on Earth, or moving objects ...
0
votes
1answer
93 views
Effect on mass of Earth if it stops revolving around Sun
If the object in motion gains mass, will it affect the change in mass of Earth if it stops revolving around Sun, since mass is responsible for gravity how will be the gravitational force change?
6
votes
2answers
186 views
Is the gravitational potential of a planet in orbit always equal to minus the squared velocity?
Say a planet (mass $m$) is orbiting a star (mass $M$) in a perfect circle, so it is in circular motion.
$F=ma$ and the gravitational force between two masses $F=\frac{GMm}{r^2}$ so
...
2
votes
1answer
88 views
Forces: Worth worrying anything?
I am a general physics student, I had a question in my text-book and according to it two students having gravitational attraction between them = ($6.67\cdot10^-8\ \mathrm{Nm}^2/\mathrm{kg}^2$) is not ...
1
vote
1answer
205 views
Gravity force strength in 1D, 2D, 3D and higher spatial dimensions
Let's say that we want to measure the gravity force in 1D, 2D, 3D and higher spatial dimensions.
Will we get the same force strength in the first 3 dimensions and then it will go up? How about if ...
3
votes
2answers
232 views
Will two trains running along the equator in opposite direction experience same wear out?
Two identical trains, at the equator start travelling round the world in opposite directions. They start together, run at the same speed and are on different tracks. Which train will wear out its ...
5
votes
1answer
355 views
Classical 3-body problem
There is a formulation of the classical 3-body Newtonian problem reducing this problem to 6 equations (e.g. http://www.3bproblem.blogspot.com). I would like to know where can I find a discussion or ...
2
votes
1answer
125 views
How does one measure Earth's speed of revolution around the sun?
I know that there are several formulae that one can plug numbers into to arrive an estimate of Earth's speed around the sun (Kepler's third law for instance), but I'm wondering how these things are ...
1
vote
3answers
131 views
Dynamics of a Rocket
I am interested in modelling the trajectory of a rocket from the Earth to the Moon by solving a differential equation numerically. Below are some key facts and assumptions I am using. I want to make ...
4
votes
2answers
114 views
What is the mass distribution within the sun?
Jupiter is roughly 1/1000 the total mass of the sun. To get some idea of what effect Jupiter's gravity may have on the sun I'd like to know the approximate mass distribution of the sun. (i.e) the ...
1
vote
0answers
73 views
Integration question from book “e: The Story of a Number” by Eli Maor [closed]
In the book 'e: The Story of a Number', a derivation of a parachutist problem is given on pg. 109-110. A parachutist jumps from a plane and at $t=0$ opens his chute. At what speed will he reach the ...
3
votes
1answer
113 views
What is the physical meaning of a flux of gravitational field in classics?
I've stumbled upon an answer to a question about square power in Newton's law of gravity. After reading it I got a question whether the flux of gravitational field has actually any physical meaning.
...
