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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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Why do planets revolve around Sun in elliptical orbits? [duplicate]

Let’s consider two planets of mass $m$ and $M$. They both will attract one another with a constant force $F$ according to the law of attraction $F=G m M/r^2$. The force and masses are constant. $G$ is ...
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Gravitation and escape speed [closed]

I applied conservation of energy at the surface and at the centre of earth which brought me to equation $$- \frac{GMm}{R} =\frac{1}{2} m v^2$$ Having asked my sir, he said that gravitational potential ...
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Has the “osmium spheres” gravity example ever been done?

Calculating the motion of two dense spheres (in a frictionless vacuum) due to gravitational interaction is a classic physics problem that has come up numerous times. Has any real-world space mission ...
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How is Gravity created in opposite to centrifugal force?

Wikipedia points out that Gravity is: most accurately described by the general theory of relativity (proposed by Albert Einstein in 1915) which describes gravity not as a force, but as a ...
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Two-body problem - point of closest approach

I am reading through an exercise : One of the hints to solve this problem is that at the point of closest approach the comet's velocity must be tangential only, why is this the case ?
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Equation for $N$-body problem using Jacobi Coordinate

For reference on Jacobi Coordinate used for solving 2-Body problem, I referred Wikipedia Jacobi Coordinate, and on looking at those equation I can't get the meaning of the symbol q in the equation for ...
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Lagrangian two body gravitational conserved quantities

I have the Lagrangian for two gravitationally attracting bodies: $$ L ={\frac{1}{2}}M\dot{R}^2 +\frac{1}{2}{\mu}\dot{r}^2 + \frac{Gm_1m_2}{|r|}$$ Where M is the total mass, mu the reduced mass and r ...
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Radius of the Sun

Is it possible to calculate the radius of the sun with minimal amount of physics? I couldn’t find resources on the internet that gives me an answer using a theoretical formula. You are given values ...
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Potential Energy equation is wrong as $mg$ force acting upwards (by us) and gravitational force ($-mg$) get cancelled and no movement is possible [duplicate]

In physics, the potential energy of an object is mgh. We say that the potential energy of an object is equal to the work done on it to make it reach that height. So the work done = mg h. Mg is the ...
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Gravity breaks Newton's third law?

Consider a thought experiment where there is a point mass M present in empty universe. Then another point mass m materializes (This is ONLY a thought experiment) at a distance of 1 light year from M. ...
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Gravitational Fields

I've been trying to understand a bit more about how gravitational fields work. I am trying to understand what would happen in the following hypothetical situation: astronauts are on the moon, and ...
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What is the direction of gravitational constant?

Our book says: $$\vec F=\dfrac{GMm}{r^2}$$ If Force is a vector quantity, $G$ must also be vector quantity so what is the direction of $G$. I am a school kid please explain simply and kindly
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Is there any model explaining why would a particle revolve around another one in an elliptical orbit? [duplicate]

The reason for asking this question is to understand the elliptical orbits of planets and why aren't they circular, we know that if a particle moves with an initial velocity perpendicular to the ...
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Orbits of satellites

For a satellite orbiting the earth, if there is only gravitational force acting on the satellite, does it mean it can only orbit the earth around the equator or through north and south poles? (only in ...
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What is the minimum mass for an object to exert a gravitational force over a smaller object? [closed]

Example: due to the earths size it exerts a gravitational force on a car, if in an isolated environment with no other objects, would a bowling ball exert a gravitational force over a piece of dust? Or ...
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Objects coming together due to small gravitational attraction

Theoretically, if I place two objects, say, 3 feet apart would they be touching thousands of years later due to the gravitational force, GM/r^2, they exert on each other?
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Gravitational Potential Energy between atoms within the same object

How can you calculate the gravitational potential energy (GPE) of just one object? I learned that there must be at least two masses in order for gravitational potential energy to exist, but any object ...
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3answers
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What happens if the gravitational force mg is greater than the normal force?

We know that the earth exerts a normal force equal to our weight on us . Now if somehow we harness the normal force and use it to do some other work (for example to produce electricity) then what ...
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Can i use gravity to represent gravitational force?

Deduction for gravity: (in both deduction, m is consider to be a point mass) deduction 1: On the surface of the earth, gravitational force FG can be separate to two force component : mg(gravity) and ...
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1answer
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Definition of gravitational field strength

The definition of gravitational field strength states: gravitational field strength is the force experienced per unit mass by a small test mass at a point in gravitational field. It can be given as $g ...
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5answers
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Work done in the presence of gravity

Consider a system where a block is to be raised from the ground to a height of 1 meter above the ground. It is given that when the force acting on the block and its displacement act in the same sense, ...
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5answers
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Do orbiting planets have infinite energy?

I know that planets can't have infinite energy, due to the law of conservation of energy. However, I'm confused because I see a contradiction and it would be great if someone could explain it. ...
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How to deal with constants on computer simulations? [closed]

I'm beggining learning about natural simulations on my courses and I had a few questions about time, and especially with the game "Universe Sandox²". I know about the basic Newton's formulas about ...
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What's the nicest proof that two isolates masses orbit their center of mass? [duplicate]

Although it seems intuitive, I haven't found proof of this fact in my textbooks from a purely mathematical standpoint. I was wondering if anybody knows of a particularly elegant proof of this fact, ...
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Where is the location of centre of gravity of the Earth? [closed]

Take the Sun as a point object at the origin. Take the Earth as a sphere centred at $x=d$ with a radius of $R$ Let $d=150,000,000,000$ m Let $R=6,400,000$ m Slice the sphere into vertical disks of ...
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1answer
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Formula for would something fall over or not?

Let's say I have a 10cm x 10cm x 50 cm wooden stick that weights 5kg total. The 10cm x 10cm base is touching the floor and it protrudes from the floor 50cm which is the height of the stick. Based on ...
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1answer
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Why doesn't the Earth slowly collapse into the Sun? [duplicate]

I understand that the sun exerts a force on the earth and that if that was the only force exerted on the earth then the earth would have already crashed into the sun a long time ago. The reason the ...
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2answers
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Gravitational force on point mass due to uniform rod

So we have a uniform rod of mass M and length L and we have placed a point mass of mass m, which is distance a away from the midpoint of the rod. Now setting the coordiates axes to work with, I put ...
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2answers
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A few questions on Gravity [closed]

What role does the unit vector $ \mathbf{e}_r $ play in $$ \mathbf{F} = - G \dfrac{Mm}{r^2} \mathbf{e}_r$$ and why there's a negative sign? If the gravitational force always acting in the same ...
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1answer
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Human Body Upward Acceleration on Scale [closed]

I am reviewing for a Physics exam, and have come across the following example question: If I weigh 200 pounds, but a scale I'm standing on reads 400 pounds, then I am accelerating upward at 1g 2g 3g ...
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Large mass body on Lagrange point L4/5

Lagrange points L4 and L5 are stable for a test particle. But what happens if instead the body at L4/5 (let's call it C) has a mass significant enough that its gravitational pull on the other two (let'...
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I don't understand why escape velocity is necessary [duplicate]

I have read multiple explanations of escape velocity, including that on Wikipedia, and I don't understand it. If I launch a rocket from the surface of the Earth towards the sun with just enough force ...
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1answer
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How to reach $U = mgh$ Using Newton's Law of Universal Gravitation? [duplicate]

today i was curious about the potential energy, so, i started studying the Newton's Law of Universal Gravitation which its equation is \begin{eqnarray} U= -\frac{GMm}{r}.\end{eqnarray} Well, since i ...
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If there was a hole in the north pole to the South Pole and you jumped into it how would would you come out feet first? [closed]

If I were to dig a hole in a round sphere Say the earth starting at the north pole standing on my feet I start to dig when I come out the other side would I come out of the whole feet first or head ...
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4answers
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Kepler's third law is unintuitive

Kepler's third law states that the ratio between the period of a planet in orbit round a star squared over the average distance to that star cubed, is constant. And in the case of an elliptical orbit, ...
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0answers
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Physics behind finding center of mass of a stick like object [duplicate]

If I hold a rod with both hands wherever at opposite sides of the center of mass of the body, and bring them slowly close to each other, then the point my hands meet at, is approximately the center of ...
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1answer
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Is gravitational force different from centripetal force in projectile motion?

This has always confused me, in a projectile motion, like a cannon shooting an object, the only force acting on the body is gravitational force, which is facing downwards or more precisely, ...
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Does dark matter experience drag?

Is dark matter dragged around the galaxy by gravity as stars and groups of stars orbit the galaxy, and, if so, is its shape/distribution deformed? Similarly, would the Oort cloud be deformed by being ...
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Partition function of an asteroid gas (gravity)

Consider the classical problem (Newtonian gravity) of a large number of $N$ identical non-interacting asteroids orbiting around a big planet. I wanted to see if the problem was solvable. I wrote my ...
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3answers
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Proving that gravitational potential is work done by the object against gravity while KE increases and PE reduces

There's a person in my class who thinks that the formula for gravitational potential (-GM/r) represents the work done by gravity to move an object from infinity to any point in the gravitational field....
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What would happen if I used a jet pack that accelerates at $g$ but always upward?

I'm trying to imagine what would happens if gravity is cancelled. I assume that without air, if the effect of gravity were to disappear I would fly off Earth on a tangential line. But with the air ...
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2answers
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When would an object not be considered a point-particle in relation to gravity?

When is the Earth, for example, not considered a point in relation to gravity? I am thinking that if one was asking a question below the crust continously to the core, then this would be an example. ...
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2answers
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Is a *difference* of potential energy relative to a frame of reference?

If we consider an electrical field, or a gravitational field, and two points in this field, is the difference of potential between this two points depending of a frame of reference ? It seems to me ...
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gravitation (kinetic energy and angular momentum)

When a satellite in a circular orbit around the earth enters the atmospheric region it encounters small air resistance to its motion. then (1) kinetic energy increases (2) angular momentum decreases ...
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2answers
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Which fundamental force underlies inertia? [closed]

We learn about the four fundamental forces (gravity, electromagnetism, strong, weak). I am curious about how these four forces mediate/cause/drive everyday phenomena. In particular, it has never been ...
2
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1answer
449 views

Newton's theory of gravity is covariant under Galilean transformations

We know from classical mechanics that the gravitational field equation for the scalar potential takes the form $$\nabla^2\phi=4\pi \rho,$$ where $\rho$ is mass density (which, can depend on time and ...
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3answers
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Newtonian gravity equation / Big $G$; not duplicate from search results

EDIT: I apparently need to rewrite this from the RE's, but I'll leave it for continuity sake. Please read my replies for my point/question clarifications. There are several threads regarding big G ...
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How do you determine weights from CG when there are more than two locations

On the internet they list ways to calculate weights based on CG when there is a weight on the left and on the right of your CG. Most of the examples show a box truck for determining the weight on the ...
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1answer
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Determine corner weights of a trapezoid

Working with determining the corner weights on one axis isn't too bad. If A is to the left of the Center of Gravity and B is to the right of the Center of Gravity. You have two equations to work with....
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2answers
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Calculation of Gravitational Potential at the centre of the cube [closed]

I came across this problem in a test and have been able to come up with a solution however I am unsure if it is correct. I started by building a cube of twice the initial dimensions to bring point P ...