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

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132 views

Gravitational binding energy and integrated potential energy not the same?

Before looking up the formula for the gravitational binding energy of a uniform sphere, I simply figured that the general formula for binding energy of an arbitrarily-shaped mass distribution would be ...
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0answers
73 views

Planatary motion of newtonian force [closed]

According to the Newtons gravity we can write, $$\vec F = \frac{\hat r_{12} G m_1 m_2 }{r_{12}^2}$$ and we are well known that this law satisfies the planetary motions. What changes will we see if we ...
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5answers
2k views

How to get the angle needed for a projectile to pass through a given point for trajectory plotting [closed]

I am trying to find the angle needed for a projectile to pass-through a given point. Here is what I do know: Starting Point $(x_0,y_0)$ Velocity Pass-through point $(x_1, y_1)$ I also need to ...
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5answers
4k views

Einstein gravity versus Newton's gravity

What's the basic difference between the gravity as seen by Einstein, and that by Newton?
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1answer
110 views

Motion in a central field and angular momentum

Is it correct that for a motion in a central force field, e.g. a gravitational field, the absolute value of the total angular momentum of the particle and the component of the perpendicular to the ...
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4answers
922 views

Paradox- Object thrown parallel to the ground will never fall down

Suppose an object is thrown parallel to the ground. The gravity acts downward (ie. perpendicular to the direction of motion of the object). The work done by gravity on that object will be given by : ...
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2answers
316 views

Keeping air in a giant gravitationally-bound space balloon

Let's say a space-faring society wants to make a space station that has a large volume filled with air (or other gas), but no gravity. Using normal pressure tanks will require gathering an amount of ...
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3answers
193 views

Forces involved in a climbing jet aircraft

I have a problem with which I need help. The question is: A jet aircraft is climbing at an angle of 45° above the horizontal and is accelerating at 4.5m/s2. What is the total force that the cockpit ...
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0answers
551 views

Gravity - What happens when two objects of unequal masses fall freely towards the ground? (Revisited)

The common perception regarding what happens when two objects of equal sizes but unequal mass are allowed to fall freely towards the ground is that - both the objects make contact with the ground at ...
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0answers
36 views

Where are the L3, L4, and L5 of a hyperbolic orbit?

Do the L3, L4, L5 points exist in hyperbolic orbits? If yes, then where do they lie?
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1answer
120 views

How does physicists calculate the gravitational self collapsing force of a star?

The nuclear fusion taking place inside the stars opposes its gravitational self collapsing force. But, how does physicists calculate it? I just know the classical gravitational theory and not a bit of ...
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1answer
58 views

Is the trajectory of the Moon around the Earth stable? [duplicate]

I understand how mathematically is possible to have one object with elliptical or circular orbit around another object in space. so can I think of it as a limit cycle? If yes, then is it stable or ...
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1answer
114 views

Does Archimedes law depend of lack of matter?

I would like to know if Archimedes law take in equation the lack of matter. Fluid density at 1. An object with density of 0 (or near 0) is put in liquid, it's fixed. The external sphere where liquid ...
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1answer
33 views

induction for massive objects

We know that when two charged bodies are kept near one another, they attract the charges and induce some charge near the surface. This happens even when only lne body is charged as the charges are ...
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2answers
192 views

Two moons of Earth?

Hypothetically, suppose there is a situation where the Earth's moon gets neatly sliced into two equal hemispheres, and the force responsible for this slicing also creates a distance between the two ...
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2answers
463 views

If there is no gravity, does that mean there's no mass as well?

I have demonstrated that weight only is measured based on the gravitational pull of where you live. For example, the gravity on the surface of Mars is three times smaller than the gravity on the ...
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3answers
100 views

Why heavier bodies produce greater gravitational pull than the lighter bodies?

The basic question "Why planets revolve around the Sun?", is explained by taking into account the heaviness of Sun. The lighter bodies are considered to move around heavier bodies,as like lighter ...
4
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1answer
188 views

Understanding the different kinds of mass in gravity

On this site, the Phys.SE question Is there a fundamental reason why gravitational mass is the same as inertial mass? has been asked. See also this Phys.SE question. The 'answer' provided on this ...
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1answer
120 views

Is this object turn alone with torque inside disk of water?

This is not the original question, I changed for explain details. But now it's not possible to delete the question and now the reply is not in relation with question. I post a new question, and try to ...
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0answers
80 views

Victorian cosmology after the second law of thermodynamics but before relativity?

In the 19th century, most astronomers adopted an island universe model, in which our galaxy was the only object in an infinite space. They didn't know that the "spiral nebulae" were other galaxies. ...
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3answers
349 views

Why gravity decreases as we go under ground? [duplicate]

We all know that gravity decreases as we go upward, we also know that gravity decreases as we go inside the earth? I don't know why gravity decreases as we go downward or inside the Earth? Please ...
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0answers
32 views

The magnitude of spacecraft anomalous velocities?

That Voyager and several other spacecraft have had anomalous changes in speed is known. According to the news reports, the differences are unsettling. But just how large are these anomalies really? ...
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1answer
255 views

Why closed bottle change its weight when I put effervescence tablet?

I use several shape, several type of material (glass, metal, plastic), I use two different balances with 0.01g of accuracy. I put oil on gasket, and put upside down (like that I can see if water ...
3
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1answer
99 views

Is it possible to levitate an object with piezoelectricity?

The delay for transmit pressure depend of speed of sound in the material. A lot of piezo slip-stick actuator can generate an asymetric wave. Like the differential pressure is not the same the force to ...
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3answers
224 views

How accurate is Newtonian Gravity?

I know that really fast moving things need Relativity rather than Newtonian physics. I also know the quirk of the Mercury´s orbit. But just how much more accurate is General Relativity than Newton´s ...
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1answer
90 views

Variational principles: Meniscus

In determining the shape of a meniscus, we have to minimize the energy per unit length along the direction perpendicular to the cross-section of the meniscus: $$\frac{E}{L}=\int^L_0 dx [\gamma ...
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8answers
418 views

Why in Newton's law of gravity, we do $M_1 \times M_2$ and not $M_1 + M_2$?

In Newton's law of gravity $$F=\frac{G M_1 \cdot M_2}{r^2}$$ we do the product $M_1 \times M_2$ and not the sum $M_1 + M_2$. Why's that so?
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1answer
138 views

In a moving bus will the ball fall behind me when tossed?

Using Newton's law I have to find whether in a moving bus will the ball fall behind me when tossed in air or will come to me only or will fall in front of me. In fact there are two cases; 1- Bus ...
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3answers
563 views

Gravitational Potential Energy (GPE) to Kinetic Energy (KE) transfer in Satellite Orbits

I am stumped by a mundane A Level Physics question (teacher of physics here obviously a bit short of practice!). My colleagues and I are stumped and were wondering if any one could help us. It ...
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2answers
94 views

How Galaxy is formed?

Given the distance among stars (the most massive objective in the space) is so huge, the difference of order of magnitude is about 7. And also, since gravity is such a weak force, how is it likely for ...
11
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3answers
466 views

Can we disprove Artificial Gravity (like in the movies) with a thought experiment?

Suppose you have a Device that creates an 'artificial gravity' (AG) inside a Box, with these properties: the system does not use inertial forces (like centrifugal force) or a huge mass to create AG ...
17
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1answer
751 views

How can the Moon have such a strong effect on the ocean?

The gravitational acceleration on Earth is approximately $ 10 \mathrm{m}/\mathrm{s}^2 $. Compared to this, the tidal effect of the Moon's gravity gives a local variation in the acceleration of ...
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3answers
488 views

Gravitational acceleration on the Moon and Mars

There are plenty of formulas that use gravity acceleration of Earth. This is represented with the symbol $g$. In my school work (I am a high school student) we usually take it as $g= 9,8 \,\text ...
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2answers
226 views

Intuitive explanation of why orbits are closed?

Yesterday my brother asked me how orbits work. Suppose for the sake of the question that you are trying to put a rocket in orbit around the Earth. I explained that orbiting is essentially being in ...
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2answers
83 views

Is centre of gravity a point?

Is the centre of earth a point? If it is so, then it should attract objects both horizontally and vertically. But, it always attracts vertically. Why is it so?
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2answers
155 views

Newtonian gravity equation in a 2 dimensional world [duplicate]

I am wondering if my line of thought is correct - and thus the resulting answer to the problem above would be correct. As we know the gravitational force (of two point masses) is given by $$F = ...
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2answers
492 views

What is going on in the system? How are the formulas `mg sin(x)` and `mg cos(x)` derived?

When a load is resting on an inclined plane, there is force $mg \sin(x)$ that's vertical to the inclined plane and force $mg \cos(x)$ horizontal to the plane acting on it like this: My textbook ...
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1answer
75 views

Do all celestial objects have stationary orbit?

Do all celestial bodies of sufficient mass such big asteroids, moon, planets etc. have orbit such that the period of revolution is same as the sidereal period of that object (such as geostationary ...
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5answers
804 views

Can Helium Disappear from Earth?

Can Helium disappear? As we know Helium is lighter than air, so basically Helium fly off from Earth. Is it possible that in the future we will run out Helium?
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1answer
52 views

About Earth Gravity and its characteristics in different scenarios

Earth's gravitational field gives rise to a typical acceleration of 9.80 m/s². If you say gravity changes with altitude, then what will be the gravity at per say 8900 meters. Is there any specific ...
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1answer
273 views

Newton's Third Law Of Motion: Earth Falling to an Apple?

I 'get' Newton's third law of motion, except for one thing. We know that if we let an apple fall to the Earth, the earth will fall to the apple, because the Earth must experience the same force in the ...
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4answers
4k views

What is the general formula for a trebuchet?

What I'm really looking for is a formula for a trebuchet that I can input the desired initial velocity after launch and mass of the object, and from that figure out how long the long arm, short arm, ...
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0answers
89 views

Collision of two asteroids in the main belt [closed]

If there are two asteroids $A$ and $B$ of equal mass (and density of 3000kg/m^3), with the same semi major axis of $a=$2.2 AU with asteroid $A$ having a circular orbit and no inclination, and ...
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1answer
205 views

Finding mass density of a sphere?

If the gravitational field vector is independent of the radial distance within a sphere, find the function describing the mass density $\rho (r)$ of the sphere. I uses the divergence of $\bf ...
14
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2answers
307 views

Newtonian gravity from the holographic principle?

Can one understand Newton's law of gravitation using the holographic principle (or does such reasoning just amount to dimensional analysis)? Following an argument similar to one given by Erik ...
5
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1answer
114 views

How does one calculate where the “surface” of a gas-giant would be?

Okay, so Jupiter, Saturn, et. al are gas giants. I understand that they have large gassy atmospheres, which, due to the pressure would eventually become more and more dense as one approaches the ...
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2answers
813 views

Finding the period of an infinite length pendulum [closed]

What would be the period of a pendulum with an infinite length, assuming a non-rotating Earth? The answer is not infinity.
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4answers
567 views

How much does the Earth's rotation affect a golf ball?

When launching rockets into space, they start straight but begin to lean, I assume due to the Earth's rotation. For something on a much smaller scale, such as a golf tee, is there a measurable ...
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3answers
343 views

Is the gravitational potential of a planet in orbit always equal to minus the squared velocity?

Say a planet (mass $m$) is orbiting a star (mass $M$) in a perfect circle, so it is in circular motion. $F=ma$ and the gravitational force between two masses $F=\frac{GMm}{r^2}$ so ...
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0answers
59 views

Gravitational Behavior of Rotating Body

Consider a stick with a (ball-shaped) weight at the end of it. Let's say this stick is in a state of rotation (it's floating in vacuum) and is also in a state of translational motion. Consider a ...