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

learn more… | top users | synonyms (1)

3
votes
1answer
247 views

How does the distribution of mass affect gravitational attraction?

For example, if a planet is considered as a point mass, then an object inside the planets' gravitational field experiences an equal attraction from all of the planets' mass. However if the planet is ...
3
votes
2answers
123 views

Gravitational Strength on a theoretical flat planet

Ok, so let me clarify: a planet that overcame all structural problems with being planetary size, I.E. collapsing into a ball. What would be the gravitational strength on a flat planet with the ...
1
vote
0answers
34 views

What is the gravitational field inside a hollow spherical cavity embedded in a solid sphere? [duplicate]

Imagine a solid sphere of radius $R$. From the inside of this sphere we remove a smaller sphere of radius $r$. The sphere can be situated anywhere inside the massive sphere. How does the gravitational ...
0
votes
1answer
76 views

Relation between gravitational field and gravitational potential

The gravitational field is the negative differential of the gravitational potential. Now the gravitational potential due to a particle at a distance $r$ is $-Gm/r$ where $m$ is the mass of the ...
4
votes
0answers
19 views

What Is the Roche Limit Factor for a Tension-Free Solid Rubble Pile?

I have reached a confusion when searching for derivations of the Roche Limit, which differ in value and explanation. All equations are given of the form: $ P = r_{M} \sqrt[3]{f\frac{\rho_{M}}{\rho_{...
5
votes
2answers
3k views

Gravitational field of sphere containing a spherical cavity

I'm just struggling a little with this question: A uniform sphere, of radius $R$, contains a spherical cavity of radius $\frac14R$, whose centre is $\frac38R$ from the surface. The diameter ...
3
votes
2answers
101 views

What kind of effect would cosmic expansion have on planetary motion or keplerian orbit? [duplicate]

The question is, if two following phenomena are thought to effect to the motion of the planet that orbits a star: Celestial body is pulled by some massive star by ordinary Newtonian gravity: $$ m \...
1
vote
2answers
55 views

Use of $g$ for centripetal acceleration

I have attached an image above including the question I'm unsure of (part B) In a nutshell, a satellite is orbiting Earth at the surface. Given is $g$ and the radius of the Earth. For part bi) the ...
2
votes
4answers
282 views

Rate at which a pendulum bob slows due to air resistance?

I know that "perfect" pendulums would be able to swing forever, unperturbed by air resistance. However, since there is air resistance around us, pendulums (swinging bobs) slow down and move closer and ...
3
votes
1answer
55 views

Velocity of satellite to crash into the earth

I was reading through this post today and was very impressed by the response that was given. However, what would have to happen to the velocity in order to collide with the Earth? Velocity of ...
-1
votes
2answers
40 views

Does displacement affect force? [on hold]

I am sorry for being unclear with my previous question. The main topic of the experiment we conducted was about work. As we learned: $W = Fd$ Work, from my understanding, is the product of work and ...
0
votes
0answers
79 views

Why did Kepler thought that the Earth was hollow? [on hold]

I was researching a little about the theory of the hollow earth, since I am a mathematician I don't understand well about physics some famous scientific thought this namely Euler, Edmond Halley and ...
3
votes
2answers
136 views

On Newton's discovery of the universal law of gravitation

I'm reading Peter Collier's book on relativity and was on the chapter where he describes how Newton figured out the law for universal gravitation. This is the cannonball referred to in the following ...
6
votes
1answer
331 views

Derivation of Universal Variables

Does anyone know of link to the derivation of the Universal Variables? This is in regards to Kepler's equations. The Wikipedia link didn't have enough information for me, and the Colorado page doesn'...
1
vote
4answers
264 views

Does center of mass affect how an object falls?

Suppose you drop an object which has two ends, of which one is heavy and the other is pretty light. Will the object fall with its heavier end downward or with the lighter one? Why does it happen?
2
votes
2answers
496 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 $...
0
votes
2answers
45 views

When do two point masses orbit or collide? [closed]

Suppose we have a universe containing two point particles with possibly different masses and initial positions/velocities (with respect to some fixed reference frame). Neglecting relativity and ...
0
votes
1answer
45 views

How do gravitational sling shots work? [duplicate]

How can an object move faster after leaving the gravity of a planet, should a gain in potential energy by moving away from the planet lead to a loss of kinetic energy? Or am I missing something ...
34
votes
7answers
5k views

Why don't we feel the subtle speed change of Earth's elliptical orbit?

Earth's orbit is a slight ellipse, so to conserve momentum its speed increases when it is closest to the Sun. If the speed changes there is an acceleration. If there is an acceleration there is a ...
1
vote
2answers
80 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
5
votes
2answers
146 views

Kepler Orbits: Small Perturbations->Elliptical Orbits

A group of my physics classmates and I have been stuck on this problem. We have tried a few approaches. The problem is to show that a body following a circular orbit, when given a small radial ...
13
votes
3answers
2k views

Why is the period of rotation the same for two stars orbiting the same centre?

In a binary star system, two stars $A$ and $B$ follow circular orbits, of radius $R$ and $r$ respectively, centred on their common centre of mass $O$. The mass of star $A$ is $M$, and that of star $B$ ...
-2
votes
0answers
12 views

Newton's law - satellite position (in 2D) for specific moment of time [closed]

I’m trying designate function that calculate satellite position (2 dimensional) for specific moment of time for better understanding Newton's law of gravity. To verify my calculations I created second ...
2
votes
1answer
354 views

Could fish in plastic bags filled with water float like that?

I saw this gif earlier and it bothered me how the plastic water bags with fish in it are not submerged in water like they would if we don't do anything special with the water inside and outside the ...
2
votes
2answers
43 views

Why is $mg$ positive and $N$ negative in this problem?

In this problem: A car of mass $430\ \mathrm{kg}$ travels around a flat, circular race track of radius $178\ \mathrm{m}$. The coefficient of static friction between the wheels and the track is $0....
0
votes
0answers
16 views

Find the mass of Europa, one of the Moons orbiting the Jupiter [closed]

Europa, one of the moons of Jupiter, was discovered by Galileo in $1610$. Europa has a circular orbit of radius $6.708\times 10^5$ km and period $3.551$ days. Find the mass of Jupiter. My attempt: ...
3
votes
5answers
164 views

A question on uniform circular motion and minimum tangential velocity

I've had a bit of a crisis in my understanding of circular motion and I'm hoping to clear it up here. Would it be correct to say that the condition for a particle to be in uniform circular motion is ...
1
vote
0answers
145 views

Position vs Time Function for a Falling Object Without Assumption of Constant Acceleration [duplicate]

If you have an asteroid for example and a planet, isolated from all other gravitational influence and initially at rest with respect to each other, how would you find a position vs time function for ...
3
votes
7answers
7k views

If the earth has gravity, why don't we all collapse to the center?

I'm sorry if the answer is obvious for you guys, but why don't we all (including buildings, road, people, the ground) collapse to the center of the earth because of gravity? Is it because we have ...
3
votes
1answer
52 views

How do non-contact forces work?

One question has been bugging me ever since I started learning physics, the textbooks successfully describe the empirical observations but haven't given any reasoning behind it. What I want to ...
2
votes
8answers
13k views

Trouble understanding the concept of true and apparent weight

I need help understanding the concept of true weight vs apparent weight. I understand this much: if someone is standing in an elevator on a scale, the further up they go the less the reading on the ...
1
vote
1answer
59 views

Calculate the gravitational force between two stars having common centre

Two star of mass $M$ and $2M$, a distance $3x$ apart, rotate in circles about their common centre of mass $O$. Express the gravitational force acting on the stars in terms of $G,M$ and $x$. I ...
0
votes
2answers
664 views

Tension in string and gravitational force on bob relative strength

When calculating time period of simple pendulum (an approximation of SHM at small amplitudes) we take gravitational force greater than tension in string and resolve gravitational force in two ...
2
votes
1answer
39 views

Eccentricity of planetary orbits: What information is contained?

I'm having a little trouble understanding what makes a planetary orbit explicitly elliptical. Is it simply that the initial velocity was different from the circular orbit case for a given starting ...
1
vote
1answer
43 views

Floating in a Dyson Sphere

Consider your typical Dyson Sphere scenario. You are standing on the inner side of the sphere. You look up and see the shining sun far away. My question (or thought experiment rather) is: ...
6
votes
3answers
1k views

Can we apply Schrödinger equation in Newton gravitational potential and derive the deterministic Newton's gravitation as a special case of it

We know the solutions for wave functions of a an atom of hydrogen, and the energy values as given by spectral analysis of radiation emitted by hydrogen confirms the possible energy states as predicted ...
2
votes
2answers
116 views

Equation for a falling body including terminal velocity

I'm making an app that times how long it takes a pebble to fall, then calculates the distance it fell. I noticed that the simple $f(t) = \frac{1}{2}gt^2$ was becoming increasingly inaccurate as the ...
1
vote
1answer
29 views

How to calculate striking speed of a meteor?

A neutron star has radius $10$km and mass $2.5\times 10^{29}$kg. A meteorite is drawn into its gravitational field. Calculate the speed with which it will strike the surface of the star. Neglect the ...
1
vote
2answers
252 views

Confusion about gravity

I understand the “rubber sheet” model of Relativistic gravity is just an illustration, and beyond the initial issues of mixing three-dimensional objects with a two-dimensional representation of 3D ...
3
votes
1answer
333 views

Marvin the Martian vs. the Death Star: how much energy will they actually need to disintegrate the Earth?

According to a detailed analysis by Dave Typinski, Marvin the Martian’s Illudium Q-36 Explosive Space Modulator will require $1.711 \cdot 10^{32}~\text{J}$ to shatter the Earth into a gravitationally ...
1
vote
1answer
44 views

Change in gravitational effect between Earth and the Sun

SPOILERS FOR "INDEPENDENCE DAY: RESURGENCE" ABOUND. I just watch ID:R and had a question about a plot point. In the movie, a large alien ship, which looked to be about 10-20 percent the size of Earth ...
16
votes
5answers
3k views

What would happen if I were to fall into a massive hollow planet?

Imagine, if you will, there exists somewhere out there a supermassive planet. For some reason, this planet is only a shell of its former existence and all that is left is a crust of substantial size ...
2
votes
1answer
89 views

Gravitational field of thin 2D ring - numerical simulation

I'm aware of Newton's Shell Theorem, which states that inside of a thin ring of uniform density, the gravitational force exerted on a point mass should be zero. I wrote a quick field simulation to ...
0
votes
1answer
36 views

From where do tides get their energy [duplicate]

We all know that tides are caused by the Moon's gravity. In this process the water in the ocean gains energy (in the form of tides, which can be harnessed to get tidal energy). Where does the ...
3
votes
1answer
64 views

How can an asteroid fall to a planet?

According to the Kepler's first law, the orbit of an asteroid would be an ellipse having the planet at one of the focuses (to a good approximation). Then how come can it ever fall to the planet?
0
votes
1answer
60 views

How noticeable is the gravitational pull of a mountain range?

A massive object like a planet exerts a great gravitational pull on nearby objects. This will cause them to accelerate towards the center of the planet with the same acceleration regardless of their ...
46
votes
5answers
7k views

What does the Moon's orbit around the Sun look like?

I'm curious as to what the Moon's orbit around the Sun looks like. If there's an answer, what's the intuition for it? Here are some things I'm assuming when trying to tackle this question: The Moon'...
4
votes
1answer
51 views

Is it valid to approximate this parabola as a circle?

Suppose I have a smooth parabolic surface on the xy plane, $y=-x^2$, and there is a ball on kept on the surface at $(0,0)$. What minimum velocity should I give to the ball, tangentially, so that it ...
7
votes
1answer
78 views

Details of Newtonian Prediction for Mercury's Precession

Could anyone point me to a book or outline the methods used to actually calculate the 532 arcseconds per century that Newtonian theory apparently predicts for Mercury's precession. I am completely ...