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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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Is friction affected by gravity?

Some people said that moving a car on the moon would make the tires spin a bit more compared to Earth's. But then I started thinking that if static friction and gravity are perpendicular to each other,...
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1answer
50 views

Quantumness of gravity and Padmanbhan insight on holography

Padmanabhan (and also Klinkhammer and others) argues that even classical gravity is already "quantum"...since: $$F=G\dfrac{Mm}{r^2}=\dfrac{L_p^2 c^3 Mm}{\hbar r^2}$$ Is this "naive" argument right? ...
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64 views

Champagne bubbles and gravity

One of the influences on bubble size is the speed with which a bubble rises in a glass - this, I believe, is due to the force of gravity which acts on the liquid around the CO2. The greater the ...
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1answer
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How does gravitation work? [closed]

Why the formula is this $$F=G\frac{m_1m_2}{d^2}$$ Why masses are multiplied and devided by d square?
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2answers
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Why wouldn't the weight of an object affect the magnitude of the drag force on that object?

I ran into trouble again with a course about drag force on skiing. This is the question, and its explanation: Which of the following factors would not affect the magnitude of the drag force on an ...
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How do astronomers explain trajectories of planets?

I'm wondering how astronomers can explain the trajectories of planets because: planets spin, so have angular kinetic energy. Thanks to the mass-energy relationship this means space-time curvature. ...
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2answers
91 views

Why free-fall acceleration is considered constant rather than increasing? [duplicate]

The force acting on a body of mass $m$ is $mg$, where $g$ is acceleration of free fall ! But why should there be a #uniform acceleration of free-fall in the first place? As per Newton's universal law ...
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2answers
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What direction would an engine spin in space?

I am working on a science project in school with a friend on artificial gravity in space. We are both wondering if we could use normal electric motors, to let the outer ring move. Since there's no ...
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1answer
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Motion of bodies released form rest in a freely falling cabin

In a paper I was solving, there was a question stated as such: A narrow but tall cabin is falling freely near the Earth's surface. Inside the cabin, two small stones A and B are released from rest(...
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1answer
50 views

How is the weight of the body, zero at the centre of the earth? [duplicate]

How can even the value of g at the centre of the earth be zero and what does it has to do with the weight?
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Why, when calculating work done when a person climbs stairs, the distance is the height of the stairs but not the distance the person travels?

I was thinking, since Work Done = Force * Distance moved in the direction of the force , the distance moved in the direction of the force would be the distance of the slanted stairs instead of the ...
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3answers
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Is gravity true for every object?

Earth gravitational force pulls all the objects toward the centre of earth.But there are many instances which disobey the law of gravity. For example our blood flows from the veins situated in our ...
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1answer
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In theoretical physics, is the Graviton related to the fundamentals behind the $F = ma$ relationship?

If the Graviton transmits the gravitational force to nuclei within atoms, and an object with mass gains energy by being accelerated (change velocity / change time), does that imply that $F = ma$ is ...
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1answer
29 views

Difference in gratitational field due to lunar apogee/perigee

I am trying to answer this Phys.SE question but got an unreasonable answer: In making laboratory measurements of $g$, how precise does one have to be to detect diurnal variations due to the moon's ...
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1answer
38 views

The Earth's Equatorial Bulge [duplicate]

It is stated that the Earth is a 'squashed sphere' due to the very slight bulge at the equator. (Thought in reality it's such a small difference, it's essentially spherical) Typical values: ...
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1answer
43 views

Confirmation / interpretation of unphysical(?) Kepler orbits

The following two pictures show the Kepler orbit of two masses $m_1, m_2$, where $m_1/m_2=7/3$, as I calculated them using $$ r(\varphi)=\frac{a(1-\varepsilon^2)}{1+\varepsilon\cos\varphi},\quad\...
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1answer
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When a massive spherical shell pulses, does a clock inside in it pulsate too? [closed]

When this sphericall shell contracts or expands, the clock inside contracts and expands too? I want to know if the clock becames larger or smaller, faster or slower when the shell pulsates. This is ...
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1answer
41 views

What is the Gravitational force between 2 bodies, when their centres of mass coincide? [duplicate]

According to Newton's Universal Law of Gravitation, $F=G{\frac{Mm}{r^{2}}}$, where $M$ and $m$ are the masses of the two bodies, $F$ is the force of attraction between them, $r$ is the ...
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2answers
51 views

How can this mass go off the edge of a disk?

If a mass rests at the edge of a disk, where friction acts on it, and the disk is rotated with an angular velocity just enough for this mass to slide out, then the linear velocity of the mass $v$ is ...
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5answers
572 views

What is $R$ in the formula for escape velocity?

From the escape velocity formula $$v_e = \sqrt \frac {2GM}R.$$ Some sources say it is the distance between two objects with mass $M$ and $m$. Some examples I have read, only used radius of the $M$. ...
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1answer
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Earth as a perfect sphere and an object trying to stand still

I have imagined the Earth as a perfect sphere with uniform mass density and I put an object somewhere between the equator and the north pole at rest with respect to earth. And also in my imaginary ...
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1answer
75 views

Mercury perihelion advancement [closed]

By Newton's gravity equations 5557 out of 5600 arc sec Mercury perihelion advancement derived from other planets gravitational attraction. Whether regular asteroids striking force could explain ...
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1answer
39 views

Measured Earth local gravity

I am looking for measured data of the local gravity on Earth. I know this website (https://www.ptb.de/cartoweb3/SISproject.php). The idea is nice but it looks a bit old and I would like to have an ...
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2answers
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Free-Fall time of a collapsing Star (Spherical Symmetry/No Rotation/Classical Mechanics) [closed]

I have been trying to prove the free-fall time $(\tau_\text{ff})$ of a collapsing star, which is the time it would take a star to collapse due to gravity, in the absence of pressure or other ...
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2answers
45 views

Delta-V of Earth to Moon mission using Moon orbit

I have read this article here and it talks about the delta-v cost of travelling to and from the Moon. Importantly it says that getting to an orbit round the Moon, and docking with a space station, and ...
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1answer
356 views

How would the rotational and orbital mechanics differ on a torus-shaped planet as compared to a spherical planet?

I am making the attempt to develop some computational models of Star systems and I was wondering how the a torus shaped planet would compare to a traditional spherical planet in the context of ...
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1answer
33 views

Grassmann-odd extra dimensions and gravity

Take a world with $D=3+n$ space-time dimensions, where $n$ are extra space-like dimensions. With extra-dimensional newton gravity $$F=G_N(D)\dfrac{Mm}{r^{2+n}}$$ Can $n$ affect IF the extra ...
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1answer
36 views

Gravitationl law and angular momentum

Why angular momentum of earth is conserved about sun whereas external force are acting on earth such as gravitational force by planet
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1answer
43 views

At what rate does the typical human body sink in a swimming pool? [closed]

Let's say I'm $1.8\ \rm m$, $70\ \rm kg$ with a fairly typical male body shape. I hold on to the side of an otherwise normal but very deep swimming pool, then lower myself so that the top of my head ...
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1answer
49 views

The maths of free fall and near free fall [closed]

I saw Usain Bolt's video today and the source said that they were in a near free fall (Usain bolt races in reduced gravity) The question that came up to my mind is how the math works regarding free ...
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3answers
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Is there any naturally occurring downward force that exists on Earth other than gravity? [closed]

For a project, I was wondering whether or not it is possible to increase the net downwards force acting on an object so that you are able to manipulate its weight.
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1answer
118 views

If we have density and mass why should we have gravity?

In a cup filled with different solutions with different densities if we put objects of different masses they will sink to different layers ... and this can be explained by mass and density so what is ...
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2answers
102 views

How did Newton know that there is force between two mass? [duplicate]

Newton's Law of Gravitation states: $$F=\frac{GM_1M_2}{r^2}$$ How did he recognize that there is a force between two masses?
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What is the force being applied? (Water Pump Problem)

Lets talk about the water pump problem where you must pump water up and out of a tank and figure out how much work was needed to accomplish this. So assume we have a cubic container with length 1 on ...
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0answers
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Effect of temperature and surrounding medium in the Cavendish experiment to measure the gravitational constant [closed]

Would the results of the experiment change if surface roughness, temperature, pressure/vacuum in chamber etc. were modified? (From Sears and Zemansky's University Physics)
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2answers
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Relationship between acceleration due to gravity and mass [closed]

See http://www.feynmanlectures.caltech.edu/I_07.html: "This statement can be expressed mathematically by the equation [...] If to this we add the fact that an object responds to a force by ...
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1answer
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Mass (as a unit) has no physical property [closed]

Einstein's GR or Newton's equation uses mass as unit or number. How can it cause gravity (physical phenomena)? For any physical phenomena to occur, there must be physical/chemical/biological/etc. ...
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4answers
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How to find angle something turns as it orbits in orbital mechanics? [closed]

Short version: Take a look at this animation really quick. https://commons.wikimedia.org/wiki/File:Orbital_motion.gif The direction in which the arrows for $\alpha$ and $\nu$ is adjusted as the ...
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4answers
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How do the two different force formulae ($F = ma$ and $F = G\frac{m_1m_2}{r^2}$) relate to each other? [closed]

$F = ma$ and $F = G\frac{m_1m_2}{r^2}$ are two formulae. Aren't they measuring the same thing? How do they relate to each other?
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3answers
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Why does Newton's Third Law work for fields?

Newton's 3rd law goes like this: To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts. I ...
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3answers
45 views

Planetary Gravitational Pull

I have read that Jupiter and Saturn apparently have no surface. I have a hard time believing that a ball of gas can have such a strong gravitational pull without any kind of a solid surface. Can ...
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1answer
74 views

Is a complex Keplerian eccentricity $e=\sqrt{1+\frac{2\varepsilon h^2}{\mu^2}}$ possible?

Wikipedia provides the following formula for the Keplerian orbital eccentricity: $$e=\sqrt{1+\frac{2\varepsilon h^2}{\mu^2}}$$ Considering that a bound object means negative energy, if the magnitude ...
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1answer
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Why does stellar rotation not shred the Chandrasekhar limit?

Investigations in the 60'ies about the question how the Chandrasekhar limit is modified by allowing a self-gravitating mass of cold fermions to rotate seem to have come to the conclusion that the ...
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1answer
44 views

Speed of a body in orbital motion [closed]

I assume I'm making a silly error somewhere but I can't see how. The question is concerning two objects $M$ and $m$ orbiting each other at a distance of $r$ apart. The first part was simply finding ...
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0answers
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Analogue of $\varepsilon_0$ for gravitational mass? [duplicate]

In electric fields, we usually define the dielectric constant in vacuum as: $$K_C=\dfrac{1}{4\pi\varepsilon_0}$$ Why don't we define the gravitational analogue, "digravitational" constant: $$\Delta_0=...
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2answers
55 views

Must the minimum of the gravitational potential generated by a given charge density occur at its center of mass?

An idle wondering that falls out of some comments trying to clarify this question: Suppose that you have some isolated mass distribution $\rho(\mathbf r)$, in principle with a smooth volumetric ...
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4answers
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Does 'special relativity + newtonian gravity' predict gravitational bending of light?

It seems to me that special relativity (SR) already predicts that gravity will bend light rather than this effect being a proof of general relativity (GR). Photons have energy proportional to their ...
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1answer
70 views

How does gravity effect to aircraft in sky?

Aside aerodynamics and buoyancy, Is there a simple way to explain how gravity is negligible in flight paths using free falling body diagram? In a parabolic trajectory,we know that at max height, ...
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1answer
96 views

Tension of a string on a rotating sphere and under the influence of gravity [duplicate]

I was studying about circular motion and found a topic that is apparent weight and found an equation of apparent value of g. But I can't understand why this is written
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3answers
111 views

Is there a chance for moon to collide with earth?

I have learned that attraction between the bodies increases when it's mass increases ,if the population increases day by day and hence it can increase the mass of earth which causes attraction ...