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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 attraction between two kilogram weights [duplicate]

Imagine two weights, each of mass one kilogram, floating in outer space. Starting one meter apart, and under no forces other than their own gravity, how long would it take before these two weights ...
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Is the normal force equal to weight if we take the rotation of Earth into account? [duplicate]

In my physics class we were doing problems such that we set $N$ (normal force) $= mg$. I understand that by Newton's Third Law, if I exert a force on the ground, then the ground will exert an equal ...
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What happens to the water on the surface of the Earth if the Earth is not rotating about its axis in the Earth-Moon system?

Suppose the Earth is not rotating. As usual, the Moon follows its normal path around the Earth. Let's assume it's a circular motion and that there are no other gravitational influences. A test ...
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1answer
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Experiments in ISS

Recently a Japanese capsule brought back proteins that were created in ISS in the absence of gravity. Researchers will study them to "understand their folding better". My question is, regarding ...
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1answer
59 views

Water at 0 atmospheric pressure

Suppose I put a bucket of water on the surface of the Earth. Then somehow the atmosphere disappears. My question is: Would the water fly out of the bucket, or would it be still there? My reasoning ...
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1answer
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Digging a hole in the moon across its diameter [duplicate]

What will occur if one digs a hole in some moon/dead-planet without an atmosphere (and without a Lava Core), such that this hole shall have a 1 meter diameter and will be so deep that shall go through ...
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3answers
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Contravariant metric in Newton-Cartan spacetime

I'm interested in the geometrized newtonian gravitation or Newton Cartan theory. In every reference that I have found begins saying that a Newton-Cartan spacetime is a manifold M with some structures. ...
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How severe would the consequences be if the earth's moon were wrenched from orbit?

The old TV series Space 1999 from the early 1970s seems to have resurfaced on Youtube reminding me of something I watched as a child. It is one of those obviously ridiculous SciFi series (from the ...
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How does rotational “artificial gravity” differ from normal gravity?

I am not a physicist, just a curious mind. I was reading a novel by Iain Banks where it was mentioned, that shifting from artificial rotational "gravity" (in space, on a rotating space craft) to real ...
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3answers
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Gravitational advantage of outer planets in war

The Expanse books cover a lot of aspects of war in a situation where humans inhabit many planets and moons of the solar system. The author makes the point that, in a war situation, the outer planets ...
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1answer
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Why is ʻOumuamua traveling so slowly?

Imagine a space rock that starts at rest at the Lagrange point between the sun and our nearest stellar neighbor, Alpha Centauri. That would put it at about 2 light years away from the sun. Now, it ...
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Why don't I accelerate upwards due to reaction force? [duplicate]

Now I am standing on the ground and thinking that I exert a force equal to my weight on the ground. So as a reaction the ground also exerts a equal reaction force on me of the same magnitude and ...
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2answers
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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
57 views

Is there an Abraham-Lorentz force for Gravity?

The Abraham-Lorentz force in Electromagnetism is the recoil a charge experiences as it accelerates due to own emission of radiation. The Newtonian theory of gravity is identical to that of ...
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3answers
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The acceleration in Earth's gravity

The acceleration in earth's gravity is $9.807 m/s^2$ at my location. But is this value uniform in the entire earth? For example in the inner core or outer core. What is the acceleration in the center ...
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1answer
47 views

Gravitational potential energy with both bodies moving [closed]

When deducing the formula for the gravitational potential energy of one body in relation to the gravitational force of another body, my teacher assumed that one body was standing still. I tried ...
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8answers
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Is it possible to squat quicker than gravity?

It's definitely possible to propel your body using muscle to move towards the ground quicker than gravity. But is it possible to squat quicker than gravity? Assuming squatting from your knees and ...
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1answer
53 views

Finding G.P.E. of a system of particles

we want to calculate the P.E(potential energy) of a system containing 3particles p1,p2,p3.the point of observation is P.so now we should add up the P.E at P due to p1,p2,p3 to get the net potential ...
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1answer
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Calculating the distance between two masses with respect to gravitational force [duplicate]

Call them $m_1,m_2$. They are compressed to their center of masses, if you wish. If the initial distance at $t=0$ is $d$, is there a formula or an efficient way to calculate the distance between them ...
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2answers
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What is the relation between physical theory and physical law?

Gravitational law was explained by Newtons theory of gravity. So a law was described by a theory. What is the theory for Newton's laws of motion?
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12answers
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If gravity disappeared, would Newton's third law make everything that was pressed to the ground by gravity get pushed upwards? [closed]

If gravity disappeared, would Newton's third law make everything that was pressed to the ground by gravity get pushed upwards?
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1answer
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Rolling ball accelerating down an incline [closed]

Why rolling ball down an incline or ramp, stops on different spot everytime? I know about friction, gravitational and angular acceleration, but what makes the ball to stop on different place?
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The dropping of two identical balls without air resistance [closed]

I was thinking about this and couldn't really figure it out. You are standing on a cliff and you have two identical balls. In this case, air resistance is to be ignored. The only thing different is ...
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2answers
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Curve for fastest time down a ramp [duplicate]

I came across a physics experiment video showing three balls released from a point A, going down three different kinds of ramps leading to a point B (https://www.youtube.com/watch?v=61S0KW7e-rc) ...
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1answer
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Is it wrong to imagine the gravitational potential of a system based on the center of mass?

I was practising some questions until I stumbled upon a question. A chain of length $l$ and mass $m$ lies on the surface of a smooth sphere of radius $R>l$ with one end tied to the top of the ...
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2answers
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How do you explain the “weight” of helium?

If weight is measured as M * g (mass x gravity), then how does the "weight" of a massive helium filled balloon negative? Let's say you have a 63,000 m^3 helium balloon. The mass of the helium is ...
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1answer
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How does buoyant force react with an acceleration $g$ load?

If a blimp with a certain amount of helium buoyancy accelerated enough to perform, let say, a +2G maneuver, would the buoyant helium force scale along with the weight force? All the mass particles ...
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2answers
216 views

Energy of room. Ideal gas law

I have been following Blundel's "Concepts of thermal Physics" and I got to the derivation of the ideal gas law. And it all made sense, we made a couple of assumptions and approximations, but then I ...
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2answers
46 views

The radius of a body in circular motion

If the kinetic energy of an object in circular motion due to a gravitational force is given by: $$E_{kinetic} = \frac{GM_{object}M_{planet}}{2X_{radius}},$$ then why does radius decrease when ...
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2answers
41 views

Centripetal force and vertical motion

In regards to an object in vertical circular motion - such as a motorcycle going around a circular track, am I correct in saying that $F_\text{centripetal} \neq F_\text{net}$ ? Generally in school, we ...
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1answer
54 views

Do attraction between two galaxies count for dark matter?

We know that the uniform rotation curve of individual spiral galaxies does require presence of some form of dark entity (matter). Does the attraction between two (or more) spiral galaxies also require ...
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1answer
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Gravitational attraction between quantum particles [closed]

Let's say we have a quantum particle with mass $m$ in a 1-Dimensional box. The potential outside the box is infinite. Say that $n=2$, so that $|\psi|^2$ will have two maxima. How would the ...
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3answers
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What is the distance from the Earth where the centripetal force would equal the gravitational force?

I've been trying to find the length of an unbendable and unbreakable tether of zero mass extending off the surface of the Earth with a mass at its end, where the centripetal force would equal the ...
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2answers
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Scale readings, the definition of weight, and projectiles

For this question I would like to define weight as a scale reading. I have a conceptual question: if I leap off a scale, according to my definition of weight the scale will claim I am heavier than ...
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1answer
78 views

How do frogs and fish rain? [closed]

I saw a documentary about the rain of frogs and fish in certain areas due to water sprouts sucking them up and causing rain of frogs and fish (pretty large ones) hundreds of miles away. But how is it ...
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3answers
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Question about drop tower deceleration

I have a really basic question. If we release an object from a drop tower $700\, \mathrm{m}$ tall, the object free falls for $500\,\mathrm{m}$ and reaches a velocity of $99\mathrm{\frac{m}{s}}$. For ...
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2answers
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Why are tall block stacks so hard to make?

Consider a stack of wood chips: each 0.5cm thick and 2x2 cm in length and width. There are 200 of them all stacked on each other. For some reason they all instantly fall. Evwn though their centre of ...
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1answer
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If a galaxy forms from a spherical stationary cloud, how much of the gas will escape?

Let's ignore the dark matter legend and stay with Keplerian physics. Assuming that there is a cloud with $N$ stationary particles with the same size uniformly distributed in a sphere and they ...
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1answer
49 views

Where does the energy from tidal power plants come from? [duplicate]

Tidal power plants taps into the energy in the motion of the oceans due to the gravitational interaction between the earth and the moon, so much is clear to me. This question is about where would this ...
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1answer
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Simulating trajectory of object in a non-uniform but static gravitational field

This is a physics question, but the motivation for it comes from game design. I want to simulate the motion of an object in 2D space with several point sources of gravity (actually stars). The point ...
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4answers
946 views

Reason for inertia of motion of Earth orbiting the Sun [duplicate]

We all know the following universal truth since childhood. Earth (and other planets) orbits around the Sun. And, while I was reading this post, I found that the reason behind Earth revolution is ...
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4answers
71 views

Applying Newton's Laws in a Circular Motion

A child ties a rock to a rope and turns it around describing a circle. horizontal. My Classical Physics teacher has told me that the string cannot be perfectly horizontal, but I don't know why. I ...
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3answers
71 views

Energy of an object

When an object goes up we say that it gained potential energy but it is doing positive work on the earth so it should lose energy.Please correct me.
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1answer
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Inclined plane vector

I have a question, I need to find $P$ in the following situation. A box of mass 5kg is in equilibrium on a slope at $pi/6$ from the horizontal. I need to find the magnitude of the force in the ...
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1answer
28 views

Gravity and objects in substances

This is probably a matter of terminology and me not finding it due to the lack of it. An apple falls from a tree on the ground due to gravity. Yet, if it falls into a water pit it floats on top of ...
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2answers
66 views

Gravitationally-induced slowing-down of the spreading of a wave packet

The spreading of a wave packet is very fast in quantum mechanics: for an electron, a gaussian wave packet spreads from one angström to 600km in one second! In his famous QM book, Sakurai mentions that ...
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0answers
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How fast would the Earth have to spin to lose the atmosphere?

I have read these questions: How fast would the Earth need to spin for us to feel weightless? Why can't we feel the Earth (or being in any non-inertial frame) rotating? And it made me curious....
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2answers
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Question regarding gravitational pull between 2 objects with an object separating them

For illustration sake, envision three objects lined up in a row. The center object would be bigger than the other two. How would the gravities of the masses of the objects on the sides of the bigger ...
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1answer
51 views

(Fluid Dynamics) Euler's equation including gravity

In fluid dynamics, we can write down the Euler's equation as $\dfrac{\partial \mathbf{v}}{\partial t} + ( \mathbf{v} \cdot \mathbf{\text{grad}} ) \mathbf{v} = - \dfrac{\mathbf{\text{grad}} \; p}{\rho}...
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1answer
67 views

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,...