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

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2answers
967 views

Why aren't satellites increasing speed because of gravitational acceleration?

Satellites orbiting the earth are experiencing almost as strong gravitation as we do, but they don't hit the earth because of their velocity outwards and the earth's curvature. But if they're ...
1
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2answers
66 views

Free fall for a longer time

When I'm in free fall, I'm weightlessness for only about 1-2 seconds. Is there any way I can feel weightlessness for a longer period of time?
2
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1answer
79 views

Why does the medium affect the Coulomb's constant but not the gravitational constant?

Why does the medium affect the Coulomb's constant but not the gravitational constant? My friend said maybe the particles of the medium affect the electric field. But the net charge in the medium is 0 ...
4
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2answers
283 views

How do we age if we tunneled to Earth's core?

Scenario Suppose there exists an advanced technology that can hypothetically transport living humans to study the center of the Earth, as they goes deeper underground most of the Earth's mass would ...
-3
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3answers
82 views

I were to travel to the other side of the world then is this logic possible? If no, why?

I go straight up and stay stationary at a particular point (at a point above action of gravity) in the sky. The earth will rotate and I decide to drop down when my destination has come exactly below ...
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0answers
58 views

Force of gravity at quantum level is indetermined?

Newton's law of Universal Gravitation states that any two bodies in the universe attract each other with a force that is directly proportional to the product of their masses and inversely proportional ...
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4answers
103 views

Sun and planets orbit each other

Do not the planets and the Sun revolve in orbits around each other and the shape of the orbit depends on where the center of gravity of the system is? The greater the mass of the Sun, the closer the ...
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1answer
62 views

Two Bodies Orbiting Around Each Other and Kepler’s Laws?

If two bodies are orbiting around a central center of gravity, how does Kepler’s first law (the one regarding the ellipse) apply?
0
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2answers
159 views

Comparing the orbit radius of two spherical objects [duplicate]

Assume the mass of star 2 is 4 times the mass of star 1. Compare the radius of the orbit of star 1 to that of star 2. Possible answers: R1:R2=1:4 R1:R2=1:2 R1:R2=2:1 R1:R2=4:1 R1:R2=16:1 ...
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2answers
95 views

Does the gravitational force of one object interfere with that of another?

Assume we have two iron spheres, Sphere A and Sphere B, with identical masses floating in the vacuum of interstellar space separated by some distance from each other. The gravitational force of each ...
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1answer
164 views

Largest size of a low gravity, Earth-like planet with Volcanoes and Earthquakes?

Provided that the Solar System consists only of Sol, a planet, and the planet's moon.... How large can my planet be so that it has low enough gravity that teenage human girls trained for jumping, are ...
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1answer
38 views

Can the gravitational constant be directly measured?

The value of the gravitational constant $G$ is $6.67384\times 10^-11 {\rm m}^3{\rm kg}^{-1}{\rm s}^{-2}$. This value is used in the formula to calculate the attractive force between two objects with ...
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3answers
884 views

How do these factors affect the free fall of objects?

Take an example of two balls of different masses being dropped from about 250 meters from the ground. How do the following factors affect free fall: Air resistance. Absence of air resistance. ...
2
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1answer
49 views

Could you give boundary conditions to the gravitational potential given the density distribution?

We´re doing a project that's all about solving differential equations with separation of variables. We´re trying to find the gravitational potential given the density distribution (that has azimuthal ...
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4answers
946 views

What exactly is the mass of a body? What determines it?

The term "mass" is very common. But what does it depend on? How is it known?
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0answers
43 views

Perturbations of planetary Orbits

I have, for years, been an Astronomy and physics nerd. For the first while, I was a total astronomy nerd. Then I slowly transitioned into physics and have been, for less than a year, a physics nerd. ...
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2answers
214 views

Would a planet in a binary star system follow Kepler's Laws?

I'm thinking it would not. I am thinking Kepler's Laws were a simplification that were possible with a simple two body (sun, planet) but would not apply for something more complex (sun1, sun2, planet)...
0
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2answers
71 views

$N>2$ gravitating masses can never reach equilibrium [closed]

If you have $N>2$ point masses, each attracted to each other by the force of gravity, how could you go about showing that they will never reach equilibrium?
2
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2answers
58 views

Does the microgravity environment in highly elliptical orbits differ from circular orbits?

I think everyone understands the microgravity environment broadcast from the ISS. But the ISS stays in a fairly circular orbit, the acceleration of gravity should be fairly uniform, the altitude and ...
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5answers
2k views

In circular motion, with a constant distance, why does the mass of the orbitting object have no effect on its revolution at all?

Using Newton's universal equation and some circular motion equation, the orbiting object's mass cancels out. But can someone please explain why this is without using pure algebra?
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1answer
68 views

Why doesn't an airplane simply go up in the air and stay there?

To get where a plane wants to go for example if I wanted to go from California to Japan, why can't an airplane simply stay up in the sky and let the earth rotate underneath it? Is it the ...
0
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3answers
147 views

How high could i jump if I weighed only half as much? [closed]

E.g. I weigh 150 lbs I had a thrust device that lifted 75 pounds. How high could I jump? What if that thrust lifted 2/3 of my weight (100 lbs)? Obviously, I cant fly, but I guarantee if I weighed ...
6
votes
2answers
557 views

Before Einstein came up with General Relativity, were there serious reasons to doubt Newton's theory?

Before Einstein came up with General Relativity, was there any serious reason to doubt Newton's theory (and its various developments)? I only know about the discrepancy in Mercury's orbit, which may ...
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0answers
33 views

What is the particle distribution in Saturn's Ring System?

In watching the scientifically scream-inducing film/movie 'Interstellar', there was a shot of the spacecraft moving through the Rings of Saturn. In this shot, and in every graphical representation of ...
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2answers
107 views

Centre of Mass and tangential velocity star and planet

We have two objects - one massive star, and one planet which has a considerably smaller, but non-negligible mass, in a circular orbit about a common centre of mass. Using equation $F$=$GMm$/$r^2$ ...
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4answers
684 views

Gravitational force of a ring [closed]

Given a ring with mass $m_1$, radius $R$ and a point mass $m_2$ with distance $x$ regarding the center of the ring. How can I calculate the gravitational force of this ring ? At first glance I'd say ...
0
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1answer
36 views

What is total force in this context?

One site said the total forces is the sum of the vectors. My homework question is "A skydiver of mass 90 kg is falling with a terminal speed of 60 ms-1. What does that mean? What is the total force ...
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1answer
125 views

What's my $\mathrm dM$? Gravitational Potential inside a circle of mass

I'm trying to find the gravitational potential for an arbitrary point within a ring of uniform mass density. The point is constrained to be in the same plane as the ring. So we start with: $$\Phi=\...
0
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1answer
52 views

How to find an equation for $x$ in terms of $t$ for a particle falling under gravity with resistance given by $mkv^2$? [closed]

Okay so I have determine the velocity $v$ and displacement $x$ as functions of $t$ for a particle falling under gravity with resistance given by $mkv^2$. I have set up the equation of motion divided ...
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0answers
43 views

Explaining why planets are round [duplicate]

is it possible to prove that planets (and/or stars) are always round (elliptical if you consider the spin)? Is there a set of equation that demonstrate that fluids (after all, molten rocks "floating" ...
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2answers
492 views

Kepler's laws to determine radius of circular orbit

"In nonrelativistic limit of general relativity there is a correction to the Newtonian gravitational potential energy $−h/r^3$ with $h = αL^2/(mc)^2$, where $c$ is the speed of light, $α = GMm$ and $...
2
votes
2answers
328 views

How to solve the inverse square law equation of motion

From $$m\boldsymbol{\ddot{r}}=\boldsymbol{\hat{r}} f(r)$$ I can get $$r''-r \theta '^2=-\frac{k}{m r^2}$$ $$2 r' \theta '+r \theta ''=0$$ Now it seems that all the books tells me the method to solve ...
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2answers
272 views

Collision of two satellites

In a theoretical situation in which two identical satellites travelling around the Earth in opposite directions collided head on so that there velocities relative to the earth both became 0, would ...
0
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1answer
341 views

Calculating the first cosmic velocity / velocity for a circular orbit

Today in class we calculated first cosmic velocity using this equation $$G\frac{mM}{(R+h)^2}=\frac{mV^2}{R+h},$$ where $m$ = mass of the body, $M$ = mass of the Earth, $R$ = radius of the Earth, $h$ = ...
90
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6answers
10k views

Could we send a man safely to the Moon in a rocket without knowledge of general relativity?

I'm wondering if it's possible to send a man to the Moon using equations consistent with Newtonian gravity and without the elaborate tools of Einstein gravity. Are the predictions made by Newtonian ...
0
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1answer
240 views

What is the Jacobian matrix of Newton's law of gravity? [closed]

I am trying to come up with the gradient of a vector (Jacobian matrix) for Newton's Law of Gravity. In other words, the differential gravitational field in 3-dimension. Here's the initial Law. $$\...
2
votes
2answers
60 views

The mass/energy of an $H$-atom and the gravitational force between it and another particle of mass $m$

The gravitational force between an $H$-atom and another particle of mass $m$ will be given by Newton's law: $$F=\frac{GMm}{r^2}$$ The question is, what is $M$ here? I thought the answer would be $$...
3
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1answer
49 views

Discrepancy between integrating over a continuous mass and intuition

Looking at the first problem on the page, Physics LAB: Advanced Gravitational Forces, and I have a little confusion: I totally follow and agree with the solution presented, but I'm wondering why I ...
0
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1answer
179 views

Find the center of gravity of a system with three spheres [closed]

Three spheres are put on a table. The first sphere, whose mass is 1 kg is 20 cm away from the second whose mass is 2 kg and the third sphere is 100 cm away from the first sphere and has a mass of 5 kg:...
0
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1answer
57 views

How to Model Differential Gravitational Field from Vectors?

The tides are caused by differences in the gravitational field of the moon on the near side and far side of the earth. If I set this gravitational field as a vector field using Newton's Law of ...
0
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4answers
85 views

Is the mathematics in my answer valid? (C is the right answer) [closed]

I have a good understanding of the concepts at hand, but I'm not so good at the mathematics part. I know the answer already (C), but would like to understand the mathematical way of determining it. I ...
3
votes
1answer
106 views

Wouldn't dark matter throw off the calculation of Earth's 'light' mass and estimates of its composition?

The Cavendish experiment first determined the mass of the Earth and (arguably) the gravitational constant. However, given the ubiquitous nature of dark matter, it seems reasonable that at least some ...
2
votes
0answers
24 views

Orbits of binary pulsars. How to calculate? [duplicate]

If I may ask: How can the orbits of binary pulsar stars, with similar mass, be calculated from Kepler's laws? Considering that both large central masses must be located at their mutual foci. Also, how ...
0
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2answers
164 views

Can $F=ma$ be used to calculate ground reaction force of someone walking/running?

Can Newton's second law of motion $F=ma$ be used to calculate ground reaction force of someone walking/running?
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2answers
604 views

Why does weight affect acceleration with gravity

I'm sure this question has been asked before, but my question is different, because it can't be answered with some formulae. My question is, why do heavier objects decelerate faster when moving away ...
2
votes
2answers
116 views

General Relativity view of Newton's apple

If one considers the free fall of an object of mass $m$ from a hight $h$ in the Earth's gravitational field (neglecting air friction) from the point of view of GR, what would be the main corrections ...
0
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1answer
61 views

Where do we get the terms involving $\Phi$ in parentheses come from in the static weak field metric?

I am confused about the static weak field metric. As written in Hartle, it reads \begin{equation} ds^2 =-\left(1+\frac{2\Phi(x^i)}{c^2}\right)(cdt)^2 +\left(1-\frac{2\Phi(x^i)}{c^2}\right)(dx^2+dy^2 ...
0
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1answer
136 views

What force acts on a coin that has been tossed when it is half way to the top? and what force acts on it when it is at the top?

This is a homework question and it appears to be a misleading question. I think that the answer is gravity for both of them. The only alternative answer I have is kinetic energy half way up and ...
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4answers
7k views

Forces on a ball thrown upwards

When a ball is thrown up in upward direction, it is said that force is in downward direction. Why we don't we consider the force given to the ball to throw up in the upward direction? Is there is no ...
0
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1answer
45 views

Decreased velocity away from gravity

Say I have a particle ($G$), which has the mass of the earth (hypothetically), and I have a second particle ($P$) moving away from $G$, in a line that is not parallel to the earth. Would this line ...