# Questions tagged [newtonian-gravity]

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

2,960 questions
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### Why can't we insert gravity in the special relativistic lagrangian?

I am a math student and I have taken four-five lessons about special relativity in a course about Lagrangian and Hamiltonian mechanics, so be patient with me if my question is stupid. My teacher says ...
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### Why do we not have devices like inductors or capacitors to hold gravitational field? [closed]

I know that a capacitor can store electric field and an inductor can store magnetic field. So is there a way that gravitational field field can be stored in any such device. Also we do not have a law ...
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### Is gravitation on earth less in nighttime than in daytime?

I have been thinking on the effect of the centrifugal/centripetal forces from the orbital movement of the earth around the sun, which might perhaps affect the gravity. In nighttime we are on the ...
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### Sound and gravity

How would heavier gravity (or lighter gravity) affect sound in terms of what I hear? For example, say there is a planet that is capable of supporting human life, but it has heavier gravity than ...
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### Why is escape velocity independent of direction of projection?

However, for any body projected with a velocity less then the escape velocity, the final maximum height will vary with variation in angle of projection. But why is this not the case in case of ...
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### If gravity accelerates all objects the same, why does a ball in water sink? [closed]

I recently learned the law of universal gravitation: F = GmM / d². It dictates that all objects should fall at the same acceleration. But how is density explained ...
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### Perpetual motion using mass defect

First off, I know this wouldn't work due to it breaking thermodynamics and that there would also be heaps of energy dissipated to the surroundings, and fusion doesn't work yet, but I'm more interested ...
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### A question about Einstein's elevator thought experiment [duplicate]

In Einstein's thought experiment (if I understand it correctly) a person in a sealed elevator in space accelerating at 9.807 m/s2 would not be able to tell the difference between that and the effect ...
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### Casimir effect - gravitational influence?

Regarding the Casimir effect, is gravitational attraction too weak in order to explain the attraction between the plates?
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### Is the shell theory, at least in concept, applicable to a ring world?

The Shell Theory tells us that inside a homogeneous sphere there is no gravity. It seems to me that if you cut off the top and bottom of the sphere and leave a ring, equal in width from the equator ...
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### How much work is required to lift an object (laying horizontally on ground) to vertical position? [closed]

Consider we know mass and length of an object. Blue line is initial position and black one is final position of an object. Confused about Work needed to lift it.
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### Clarifying doubt related to gravitation inside a shell

I proved that gravitational field due to a ring would be $-GMz\over\sqrt{z^3+R^3}$ for any particle lying on the axis perpendicular to its plane and passing through centre. My teacher told me ...
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### Couldn't we always redefine units so that inertial mass and gravitational mass are equal?

It is a known fact that inertial and gravitational masses are the same thing, and therefore are numerically equal. This is not an obvious thing, since there are even experiments trying to find a ...
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### How does Sun's fusion output compare to its gravity?

How does the total solar energy output compare to the total energy required to keep it contained (i.e. Sun's total gravity). In other words, is Sun's output "positive" if its gravity is factored in ...
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### Motion of the center of mass of rigid bodies in space

For the classic two body problem, I know that the motion of the center of mass is a straight line (with respect to an inertial frame), provided that the bodies are considered as point particles. Now ...
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### What would happen if we had a crystal structure but only gravitational interactions?

The idea is simple. Let's say we arrange similar bodies (call them planets, ions, anything) in an infinite crystal structure, but the only possible interactions are gravitational interactions. A ...
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### Why do two things lose contact only when normal = 0?

Why do two things lose contact only when normal = 0? For example, I was doing a question in which a massless plank was attached to a spring. The plank also had a block of mass m kept on it. The whole ...
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### Sci-fi ships falling on planets

I hope the question is suitable for this forum.... Watching Star Trek: The Next Generation, I have found at least a couple cases where a navigation malfunction on a shuttle makes it fall towards the ...
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### Mass versus rotation Curves

Is there an equation that describes the relationship between the mass of the Galaxy and rotation curve? I found V versus R graphs and equations that describe their relationship (kind of). But I ...
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### Restricted 3-body problem - Rotating coordinate system

I'm trying to follow the formulation of the restricted 3-body problem in Taff's "Celestial Mechanics" book as I'm writing an essay on Lagrange points and am confused by the transformation into the ...
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### Electric force is stronger than gravitational force yet gravitational forces holds the Sun and planets in their orbits around the Sun [closed]

The electric force between an electron and a proton, between two electrons, or between two protons is much stronger than the gravitational force between any of these pairs of particles. Yet even ...
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### How to find gravity field of a solid square body?

I was programming gravity simulation and stumbled upon a problem, that Newton's formula for point masses is not enough for me, I need gravity field formula of a solid square body (2D). To simplify ...
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### Why $g$ is not negative in potential energy $= mgh$ formula

For eg. A boy of mass 55 kg runs up a staircase of 50 steps in 10s. If the height of each step is 10 cm, find his power. My question is here why are we not taking g as negative as boy is moving up ...
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### What is holding things like the Earth and the Sun in one dimension?

I was thinking last night: for most of my life I’ve been taught that the planets in our solar system orbit the Sun, which insinuates that the Sun is in a fixed point in 3-dimensional space, and that ...
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### Does gravity do work on suspended objects? [closed]

A block is suspended from a string; does the gravitational force do any work on it?
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### Barycenter of a binary star system

It is said that the barycenter of 11 Draconis (Thuban) and 10 Draconis which compose a binary star system is a central point. Is this central point a material or immaterial object? Does the size of ...
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### What is the shape of a stream of water coming out of pipe?

As shown in the photograph below, when water comes out of a pipe (located on the surface of the earth) it travels downwards in an arc. What is the shape and size of this arc as a function of D, the ...
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### Total Gravitational Potential between two objects? [closed]

It's taken me a while to formulate what i've been thinking about, but what is the total gravitational energy between two objects, not the instantaneous force between them? For example: imagine two ...
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I was in physics class and we were talking about the gravitational constant G (6.67 x 10^-11 Nm^2/Kg^2). The question came up: "Why does $F= (GMm)/r^2$ have a constant of proportionality and not $... 2answers 122 views ### How do you derive a quantum field theory from a spacetime metric? What are the first steps in converting a metric into a quantum field theory? I know roughly what to do once I have a pair of non-commuting operators, but how do I get to that point? Specifically, I'd ... 0answers 19 views ### Force analysis of falling spring [duplicate] As picture below, I want to explain why the bottom of spring will be motionless a little while after release. But in my view, the bottom of spring will be falling in a low speed after release, since ... 1answer 59 views ### Definition of a meter and Newtonian law of Gravity Newtonian law of Gravity: $$F_g = \frac{m_1 m_2}{l^2} G$$ $$G = 6.7 * 10^{-11} \frac{m^3}{kg * s^2}$$ A meter is defined as: the length of the path traveled by light in a vacuum in$1/...
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Let us consider the following problem: it is necessary to find the shape of the body with fixed mass and density which at large distances compared with its characteristic dimensions would give the ...
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### How would I find the angular accelertion of a disk rolling up a ramp? [closed]

I need to find the angular acceleration of a hollow ball rolling (without slipping) on a ramp, given the angle of the ramp theta, the mass and radius of the ball, and gravity and other physical ...
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### The shape characteristics of gravitational wells given different masses and spread of objects

I am curious as to research that calculates the shape of gravitational wells, and their limits, and affect on time, for different masses and spread of mass. The actual question is st the end. For ...
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### How would the path of a satellite be affected by the gravitational constant decreasing? [closed]

An artificial satellite is moving around the surface of earth. If the magnitude of the gravitational constant starts decreasing at a constant rate, then what would the effect on the path of the ...
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### Why is the tension in a pendulum string highest when it is at the mean position?

Why does the string of a pendulum have max tension when it is at the mean position?
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### Why mass has no effect on free-fall acceleration? [duplicate]

I learned that mass is a property of objects that specifies how much resistance an object exhibits to accelerate. So, pushing an object with a greater mass would cause a smaller acceleration than ...
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### Accurate Equation for Earth's Gravitational Binding Energy

This is a relatively important question for anyone who can answer it. I am trying to find the equation that accurately solves for Earth's Gravitational Binding Energy. The information below is from ...
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### Initial acceleration concerning free fall

I'm in the process of conducting research concerning free fall with air resistence. I'm dropping a beach ball filled with air from certain heigts, while measuring its speed and acceleration during the ...
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### Does mass affect how likely an object is to topple over?

I was at work recently pulling around some pallets when I had a thought. I wanted to know if the mass of the pallet had any influence on how likely it is for the pallet to topple over when going ...
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### Action reaction forces in an accelerating elevator [duplicate]

If an elevator with one man in it, is accelerating as it moves upwards, the reaction force the floor exerts on the man will be more than the weight of the man. Why is that though? Shouldn't the weight ...
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### Internal work in system made up of a ball and the earth

Assume I am considering my system to be the earth, a ball, and the gravitational interaction between them. No air resistance. Assume the ball has a nonzero initial velocity upward. I understand there ...
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### Particle in a gravitational field moving at constant speed in some inertial frame

While working on an unrelated problem I found an interesting result which I presume must already be known, but I cannot find any reference to it. It is the following: Consider a small particle P ...
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### Does relativistic mass really increase with velocity? [closed]

Suppose there are two masses on the ground $M$ and $m$. The distance is $d$. So according to newton's law the gravitational force between them is $F=\frac{GMm}{d^2}$. Now suppose that I am going ...
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### Springs and Hooke's Law

Suppose a mass was stretching a vertical spring. Why does the mass have a velocity in its equilibrium position where the net force is 0? Note the spring is massless.
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### Solar System Position and Velocity data

I'm trying to create an nbody simulator and to test it I'd like some real world data. A good test would be the solar system. I've come across the JPL Horizons software but if cant seem to figure out ...
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### Do centrifugal force and gravity differ in their effects on objects?

If the type of object matters, consider the human body. If the situation matters, consider standing on the inside wall of an O'Neill cylinder compared to standing on the surface of Earth. "Differ in ...
I calculated the location of the centre of mass of Earth-Moon system using $$\frac{\sum m_ix_i}{M} = \frac{mx}{M}$$ where m is the the mass of the Moon $= 7.35\times10^{22} kg$, x is the distance ...