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Questions tagged [newtonian-gravity]

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

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Gravitational Binding Energy

Lets define the Gravitational Binding Energy of a set of point masses as the work required to separate all point masses by an infinite amount. First Question: Is the amount of energy required to do ...
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2answers
49 views

How to calculate weight of an object on an angled surface?

What formula could I use to calculate the apparent weight of an object on an angled surface, e.g, a 100 kg box on the side of a hill at 10° given that the measuring instrument is also at that same 10° ...
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1answer
37 views

Violation of Gravity as a Conservative force?

I was trying out a simulation about escape velocity to understand why direction has no impact on it here :http://highered.mheducation.com/olcweb/cgi/pluginpop.cgi?it=swf::800::600::/sites/dl/free/...
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1answer
740 views

What are the tidal effects of Io on Jupiter?

I recall reading an essay by Asimov (I think) around 1980 stating that the tides are a function of a power of the diameter of the primary, so (surprisingly) small close moons of Jupiter raise large ...
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5answers
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Kepler's 3rd law: ratios don't fit data

I have been looking at satellite orbits around the earth, or any object around any planet in fact, and am trying to find the orbital radius, or semi major length of a given satellite. Kepler's third ...
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4answers
222 views

If F(action) =F(reaction), why doesn't a ball bounce to its original height? [duplicate]

This might seem like a very absurd/ridiculous question, but this question suddenly popped on my head a few days ago. Is it that I'm missing something as I haven't reviewed this topic for quite a while?...
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2answers
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Why is the resolution or measurement uncertainty of $G$ so bad?

I sorta know how the Cavendish apparatus works, and I know that "Gravity is an extremely weak force" for subatomic particles in comparison with the E&M or nuclear forces that act on these ...
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How do you determine the path of a particle placed in a vector field?

I have recently found a way of expressing newtonian gravity as a vector feild. First the Equation $$F=\frac{Gm_1m_2}{r^2}$$ I only want to know the accelleration in the equation since I only want to ...
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1answer
25 views

What imparts the linear motion or the tangential velocity to natural satellites like the moon to enable them to be in orbit around the earth?

From Newton's laws of motion & gravitation, it is clear that the force of gravitation provides the necessary centripetal force which acts along the line joining the centre of masses of the earth &...
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24 views

Why does the Earth not fall towards the Sun? [duplicate]

According to http://wtamu.edu/~cbaird/sq/mobile/2013/07/01/why-doesnt-the-earth-fall-down/ , the earth does not fall down because of the gravitational force of the sun. At the same time , earth's ...
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A body is launched at a height of $8R$. Which of the following are correct? [on hold]

a body is launched at a height of $8R$. which of the following are correct? check the image for detailed question and correct answer and provide detailed solution
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Inverse square law not accurate for non-point masses?

It would seem that the inverse square law, popularized by Isaac Newton, is only true for masses which have no dimensionality and are a single point. In other words, it is only an ideal, not a ...
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3answers
57 views

Kinematics and dynamics of a crashing satellite

A satellite in low, circular orbit around the Earth experiences drag (friction) and slowly spirals into Earth's atmosphere. It then enters the Earth's atmosphere, heats up catastrophically and burns ...
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2answers
73 views

Friction and satellites

There was this question we did in class. There is a satellite orbiting the Earth. It runs into some particles, and due to friction, the satellite loses speed. We were asked to predict what will happen ...
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2answers
152 views

Why the time period of pendulum with infinite length is $84.6$ minutes? [closed]

In a book I was reading about SHM it stated: If the length of a simple pendulum is increased to such an extent that $\ell\to\infty$, then its time period is given by, $$T=2\pi\sqrt\frac{R}{g}\...
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1answer
20 views

Formula manipulation [on hold]

What is the potential energy of a metric ton (1000 kilograms), 3 meters above Earth's surface (at sea level), expressed in Kilowatt Hours? Assume that the mass will end travel when it contacts Earth. ...
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Is Frictional force on each block 3kg or 12kg? [closed]

Two blocks P and Q of masses m1= 2 kg and m2 = 4 kg are connected to a third block R of mass M as shown in Fig. 3.16 For what maximum value of M will the system be in equilibrium? The frictional force ...
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1answer
406 views

Does gravity affect water permeability?

Suppose I have an approximately rectangular prism composed entirely of folded paper. If I place 600lbs on top of these rectangular sheets of paper, the paper should compress. How does this affect ...
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5answers
176 views

Can gravitational constant be changed?

In my book(Principles of Physics by Resnick,Halliday,Walker) , the authors write: If $G$ - by some miracle - were suddenly increased by a factor of 10, you would be crushed to the floor by Earth's ...
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0answers
31 views

Gravity and propulsion [closed]

If a body (m) weighs 200 lbs (90.7185 kg) at sea level and gravity diminishes as the distance between it and the earth (M) increases, what would the body's relative weight be at an altitude of 128,000 ...
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1answer
40 views

Nonlinear GPE of a solid block seems wrong

I am trying to calculate the gravitational potential of a solid block, and I have a nonlinear answer which strikes me as wrong. A block with horizontal surface area $A [m^{-2}]$ and uniform density $\...
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6answers
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Acceleration in free fall [duplicate]

A body in free fall "feels" no gravitational force (equivalence). Why does it continue to accelerate. Why is your program refusing my question?
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3answers
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Force due to motion around Sun [closed]

Think of one person on earth named A . Ignoring Earth for a second, I can imagine him moving around the Sun due to which he should always feel some acceleration towards Sun (Centripetal Force) say F1. ...
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1answer
86 views

State of $N$-body system after time $t$ (under gravity and inelastic collision)

Given the centers of gravity of $n$ spherical bodies of unit mass, $p_1$, $p_2$, ...$p_n$, and assuming perfectly inelastic collisions, how does one find the location of the bodies after time $t$? ...
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0answers
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Gravitational potential energy of an isothermal sphere

I am trying to calculate the gravitational potential energy, W, defined as: $W = -\frac{1}{2}\int\rho(r)\Phi(r)d^{3}r$ for an isothermal sphere. I am given that the density profile varies with r as:...
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1answer
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About Kepler's laws [closed]

Yesterday I was reviewing some calculations using Kepler's laws and when working the third law that relates orbital periods and distances, it is very normal that, given the parameters of some object ...
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0answers
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Reference Frame conceptual confusion

I am getting confused as to why a ball still feels gravity when inside a moving car. The point of a reference frame is to reinterpret all the forces acting on a particle in one frame only. Hence all ...
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1answer
25 views

Kepler papers (2-body problem) [closed]

Where can I find papers by Kepler? I am looking for his solution to the two-body problem.
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0answers
42 views

Gravitational potential of an infinite plane

In this link http://www.feynmanlectures.caltech.edu/I_13.html#Ch13-S4 , Feynman first computes the gravitational field generated by an infinite plane of constant density, and then he computes the ...
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2answers
423 views

Boundary conditions in Poisson's equation for gravity

Say we want to calculate the gravitational potential everywhere around(outside) a solid, circular, right cylinder. We want to use Poisson's equation for gravity for that (Laplace(U) = -4*pi*density ...
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2answers
367 views

Gravitational Potential Energy and Zero Points

I have two questions. 1) The first one has to do with the formula for deriving Gravitational Potential Energy. I learned that, for the derivation of Gravitational Potential Energy given large ...
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3answers
78 views

Potential energy of an oscillating pendulum

The following question always confuses me. for an oscillating pendulum why the potential energy is given by: $$V = mgL(1-\cos\theta)$$ Why not $$V = mgL\cos\theta$$ Is this a convention or there ...
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2answers
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Would equal balance at same height when hung on a balance?

This is based on a question from the gravitation course on Brilliant. As you can see in the diagram below, we have 2 weights hung on a pulley. It is given that: Neither one accelerates when you let ...
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2answers
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How to find Lagrange point $L_2$ of the Earth-Moon system?

I was tasked in my programming lesson to find a value of L1 correct to 5 significant figures, but in my discussion section I began to wonder why there was no second solution to the equation I was ...
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1answer
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How does orbiting work exactly? [duplicate]

First of all I'm not a physicist or anything and I don't know much about physics, so I'm sorry if this doesn't make sense at all :) And if possible please try to explain it with words instead of ...
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0answers
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Compression of air layer by parallel planes

When object is falling and close to the ground "liquid pillow" appears under it. Object is of cylindrical form. The differential equation that describes the motion is: $$m\frac{dV}{dt} = mg - \frac{...
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1answer
42 views

Which ball touches the ground first? Different explanations

Two balls with the same shape and volume but very different masses are dropped from the same height WITH air. The heavier ball should land first, but is it because of terminal velocity (see this ...
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2answers
68 views

Question About Gravity vs. Earth’s Rotation [duplicate]

If a bullet was fired perfectly straight up (assuming a windless environment) such that the peak of its trajectory was just shy of orbit, would it fall back to Earth in the same spot, or would Earth’s ...
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8answers
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“Falling upward” - how far you have to be from Earth to start falling to the Moon?

Talking about gravity with my 9 y/o she asked when do we start "falling upward" to the Moon. What is the distance at which the Moon's gravitational attraction is higher than that of the Earth and thus ...
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2answers
159 views

Gravitational/centrifugal effects felt in a space elevator

I understand that a space elevator should be at least as long as a geosynchronous orbit (22,236 mi), because only beyond that is the centrifugal force from the Earth's rotation is greater than the ...
5
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1answer
76 views

Would a universe with special-relativistic gravity make sense?

Coulomb's law in electrostatics in analogous with Newtonian gravity. It's pretty clear neither of these can be used in a universe that obeys special relativity. They both must be modified to avoid ...
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4answers
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Why does oil float on water?

This might be a silly question but I want to know why oil actually floats on water. I tried to explain it to myself using Archimedes' principle but that didn't help. Archimedes’ principle, ...
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0answers
46 views

Apple shape with no gravity [closed]

Would the shape of an apple change if it grew with no gravity? I would expect it having a slightly narrower and deeper dent where the stem is attached but I cannot quite figure out how to estimate ...
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0answers
38 views

Newtonian Limit of the Accretion Efficiency of a Black Hole

Netzer's book "The Physics and Evolution of Active Galactic Nuclei" (Cambridge) gives, in Section 3.2, the efficiency of a Black Hole (BH) in converting rest mass to electromagnetic radiation as: \...
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2answers
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Does the apple fall towards the earth or does the earth move up to the apple? [duplicate]

Does an apple fall towards the earth or does the earth move towards the earth?...but if this is true then in the opposite side of the world would have to move towards them as well.
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5answers
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How the apparent weight varies due to the rotational motion of Earth?

I learned that as the earth rotates about its axis, the bodies on the earth also follow a circular path. In most books I read, they give the example of a person standing on a weight balance at the ...
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2answers
148 views

Escaping the Gravity well of the Moon

How much energy would it take to get 1 kg from the Moon's surface to Earth? Would You aim for Lagrange Point 1 or would you launch in the opposite direction that the moon is orbiting?
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How to derive the gravitational potential on an infinitely thin disc of finite radius?

I am stuck on a problem that requires me to calculate the gravitational potential on an infinitely thin disc of finite radius $R$ with mass $M$. This infinitely thin disc models a galaxy. Once I have ...