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

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Center of gravity of a hollow tank

I have to find the center of Gravity of a hollow oblong tank with 1 side missing. For installing lifting lugs x 4 on top which must align with the intersection point. (the tank will be lifted off the ...
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38 views

Point of zero gravity for fixed masses?

Given a number of fixed point masses in 3D space, is there necessarily one or more points where there is zero gravity (ie, the combined gravity of the masses cancels out), and, if so, how do I find ...
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155 views

What would become of the earth's orbit if half of the sun's mass were suddenly to disappear? [closed]

I shall assume that the sun is at rest, so before the half mass disappear, the orbit of earth is an ellipse.
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1answer
31 views

Sitting to Standing Posture Transition Accelerometer Triaxial Data Explanation

I don't have a physics background. (I'm a Computer Science student) I have a waist-worn accelerometer provided by the school which is quite reliable. I've captured data of sitting still to standing ...
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57 views
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32 views

How gravitational force works for higher mass body with distance

$$F= \frac{G(m_1m_2)}{r^2}$$ This is the newton's universal gravitation law. Here, I want to ask how does a very very higher mass body affect the smaller body, whereas they are far away from each ...
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2answers
100 views

Time period of a satellite close to earth

The time period $T$, of a satellite revolving around the earth and close to it is given by, $$T = \frac{2\pi r}{v}$$ where $v$ is the linear velocity of the satellite and roughly equal to $8\ \mathrm{ ...
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1answer
36 views

Why is the gravity in a mine shaft independent of depth if the local density is 2/3 of the average density? [closed]

While searching for something, I have come across the fact that the gravitational acceleration in a mine shaft is independent of depth if the local density is $2/3$ of the average density (of the ...
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44 views

What motion does this experience?

I have two Earths of $x$ distance away from each other. I place a spacecraft perpendicular to the centre of mass and the distance between the two Earths. If the Earths are fixed, then the spacecraft ...
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1answer
41 views

Minimum energy required to remove the satellite from its orbit to infinity?

My book says that minimum energy required to remove the satellite from its orbit is equal to its total energy (K.E+P.E). But shouldn't it equal to only the potential energy difference of satellite in ...
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3answers
155 views

When does normal force equal to $mg$?

Can someone once and for all explain when does normal force equal to mg? I know for sure that when there is no friction, normal force will be equal to mg. But, i encountered some questions when there ...
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1answer
83 views

Would an object falling on the surface of the Sun look like this? [closed]

I've been playing around with some rustic animation and then I came to simulating gravity over squishy objects, I simulated a squishy ball of unknown "squishiness" (I'm sorry I don't know a lot of ...
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5answers
112 views

What in nature causes Newton's gravitation constant to have it's given value?

Does the value of Newton's universal gravitational constant $G$ remain a mystery? Why does it have the value that it has?
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103 views

Le Sage's Theory of Gravitation, is “drag” the only reason why this theory fails? [closed]

Le Sage's Theory of Gravitation was originally proposed allready 1690 by Nicolas Fatio, and has ever since been studied by remarkable scientists; Leonhard Eluer once remarked that it was "infinitely ...
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25 views

Why is normal force at a different location than its action forces (ie, seesaw)?

It seems very counterintuitive that the forces at the two ends also constitute the normal force at the pivot point. Does this principle apply even if the plank is tilted? (It would be good ...
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0answers
29 views

What is exactly gravitational potential energy and explain P.E. $= -GMm/r$? [duplicate]

I was studying gravity and I came to know about $P.E.= -\frac{GMm}{r}$ which is derived by $GMm(\frac{1}{\infty} - \frac{1}{r})$ which the work done by the body to displace it from infinity to $r$. ...
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About a cloud of charged pallets fired toward the earth

We assume there is a spacecraft that points directly to the center of the earth and it is at about 1 mil. km away from out planet. The craft has a plastic gun filled with a lot of charged plastic ...
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2answers
178 views

Does Newtonian physics work on a galactic scale?

I'm currently working on a simulation that aims to use Newton's Law of Gravitation to simulate how a galaxy behaves gravitationally. While I haven't gotten the simulation finished yet, I have had a ...
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0answers
48 views

Are these two equations correct? [closed]

I know this is a pretty simple question, but like there should be room for those as well. I have the following two formulas describing how long it'll take for an object to decelerate. For example if ...
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69 views

Can a Set of “Maxwell's Equations” for Newtonian Gravitation be Derived from Newton's Force + Special Relativity?

When I learned about electromagnetism in my first year of undergraduate school, Maxwell's equations were derived roughly in the following way (see also here or in [1]): Gauss's law for a static ...
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49 views

Deriving Kepler's First Law from Newton's Law of Universal Gravitation: Interpretation of the $u = 1/r$ change of variable

I'm working through a somewhat unsatisfying derivation of Kepler's First Law from Newton's Law of Universal Gravitation. The key to obtaining the equation of motion that you can solve lies in making ...
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4answers
443 views

Gravity between two unequal masses. Do both masses move?

I've been watching videos about gravity and I have a question My understanding is that mass have gravity and gravity is a force which attract other object with mass. For example, I jump up and the ...
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1answer
65 views

Why can center of mass be used in calculating gravity?

Why can gravitational forces be based on the center of mass. Due to the fact that gravity is related to the square of the distance should not the gravitational sum of every particle exceed the force ...
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45 views

Hammer will fall faster than the feather on the moon. 10 second thought experiment! [duplicate]

Please explain where my logic is wrong. a) Ignoring air, the same bowling ball will fall faster on Earth than on the Moon. b) Now, for the feather and hammer on the Moon, reverse your point of view ...
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2answers
95 views

Why is the acceleration due to gravity $g$ quoted as if it were constant?

In elementary physics courses the value $g=9.8\:\mathrm{m/s^2}$ is used almost universally. But surely this value must depend to some extent upon one's location on the Earth. Why do we assume a ...
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32 views

Expression for the energy in the limit case of weak gravitational field

I'm trying to solve the following problem of General Relativity. Consider a particle of mass $m$ which moves following a geodesic in a space-time with metric $$ ds^2 = - ...
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3answers
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Law of gravitation

How can I prove the Newton's Law of Gravitation wrong? I saw 2-3 videos but could not understand. What are the flaws that Einstein came up with in Newton's Law of Gravitation?
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Could we launch a missile from a planet with the mass of Jupiter?

If the Earth had the mass of Jupiter, would we be able to launch a space missile ? Is there a formula to calculate how the launch of 1-Kg payload increases with gravity?
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46 views

Direction vector for gravity

I have co-ordinate axes on the earth's surface (and I've been told these are the axes I have to use). Ignoring z, I have x and y axes. The question asks me to calculate the acceleration due to ...
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1answer
35 views

Why does the Moon have circular motion while a falling apple has one-dimensional motion? [duplicate]

An apple and the Moon are both attracted to Earth. So why does the Moon have circular motion while an apple has one-dimensional motion?
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3answers
785 views

In which direction, the force of gravity directed towards?

I am not being able to answer, where is actually the force of gravity directed towards ? Look at this picture. This is a planet with the centre ‘C’. And O is an object. Every point of the planet ...
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1answer
53 views

Is gravitational acceleration truly independent of mass?

I am doing Newtonian Physics. Correct me if I am wrong: So two objects always exert equal forces on each other(Newtons Third). So for example the same gravitational force that the earth exerts on a ...
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1answer
62 views

If Earth was split into thousands of astroid-size chucks, would any of them have gravity? [closed]

I know that mass increases gravity and that less mass decreases gravity. But is there a minimum gravity amount that won't let meteors or astroids have gravity because of their littler masses?
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21 views

Equation for Turning Projectile

I'm trying to cook up an equation that will give me position for a projectile which operates in the Newtonian Domain. So a the fall equation is: $$\mathbf{p_t} = \frac{\mathbf gt^2}{2} + ...
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45 views

A Magnetic Vortex in a Magnetic Vortex

This is not to scale. Can a magnetic vortex be compressed into a flat disk using magnetic entrapment? Can a magnetic vortex happen inside another magnetic vortex?
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5answers
139 views

Does gravity acting on a resting object produce any heat?

Let's compare two systems. System 1: A box is completely isolated. There are no forces acting on that object, and no interactions of any kind with other objects, waves, etc.. System 2: The same box ...
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32 views

Lunar orbit homework question

So what I did was find the potential energy of the lander at the 50km orbit and the 300km orbit, then I took the difference between the 2 potential energies and I though that would be the work done ...
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2answers
81 views

Is gravitational potential always defined for a system?

I have studied about Gravitational potential energy ($GPE$) and Gravitational potential ($GP$). ..while everywhere it is said that $GPE$ is always of a system as it depends on the configuration of the ...
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73 views

Does an object decelerate when reaching terminal velocity

I'll take the sky diver example. Right when a sky diver jumps out of the plane the net force of the diver is greatest. Then the diver begins to reach terminal velocity where the force of resistance = ...
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2answers
102 views

What general relativity predicts in such a situation?

If there's a system of a point mass or point particle with mass 'm' and a structure such that - The structure is made of many concentric spheres (shells) with certain thickness and the radius of those ...
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3answers
114 views

What is the distance between two objects in space as a function of time, considering only the force of gravity? [duplicate]

What is the distance between two objects in space as a function of time, considering only the force of gravity? To be specific, there are no other objects to be considered and the objects in question ...
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1answer
52 views

Why does Goldstein's derivation of orbits from Newton's law not yield the orbit consisting of symmetric oscillation along a line thru center of Sun?

Why does Goldstein's derivation of Keplerian orbits from Newton's law of gravity not yield the orbit consisting of symmetric oscillation along a line passing thru the center of the Sun? The fact that ...
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2answers
129 views

Defining gravitational potential

I recently came across the definition of gravitational potential where ..... Suppose a particle of mass $m$ is taken from a point $A$ to $B$. Let $U(A)$ and $U(B)$ denote the gravitational ...
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1answer
89 views

Confused by gravity and weight [closed]

I know that $F = mg$ so $2,00 \textrm{ KG m} \cdot 9,81 \textrm{ N g} = 19,62 \textrm{ N F}$ Why does my book say that the weight of a $2,00 \textrm{ KG}$ object is $19,62\textrm{ N}$, the mass is ...
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2answers
87 views

Center of mass chaotic in n-body gravitational interactions?

I wrote a gravitational particle simulation. To prevent the particles flinging off out of the screen, I added a bit of friction (it also makes the animation prettier as particles spiral into one ...
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1answer
35 views

Calculating position of a particle at time $t$ in a gravitational field

I'm working on a piece of code that is supposed to visualize a particle bouncing up and down from the ground (somehow magically we can give it velocity upwards when it is on the ground). I figured ...
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0answers
43 views

Finding position with respect to time along a trajectory across a sphere (orbital mechanics)

When trying to find an object's position with respect to time on a ballistic trajectory along a curved surface, what equation should I use? I know that when adding force to an object to achieve ...
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68 views

Compute the gravitational force between two vertical rods [closed]

My AP physics teacher posed this problem at the end of his lecture today and I want to be sure my physical set up is correct (I've already done the math, but just double checking!). The situation is ...
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2answers
61 views

How do gravity anomalies on Earth comply with conservation of energy?

Gravitational acceleration varies from place to place on Earth in a range of about 0.02 percent and is caused by density distributions within the Earth. Imagine an experiment where you move around the ...
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4answers
2k views

How is hydrostatic pressure overcome when a star is formed?

If stars are formed by the collapse of dust clouds under gravity, how is the pressure of the dust cloud overcome? As more material gathers together, gravity will increase, but pressure will also ...