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

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330 views

Is it possible to have things orbit around us?

Since humans are not large in mass, do we exert enough gravitational force for a small object to orbit around us? (Assuming that the only gravitational force acting on the object is from the human). ...
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2answers
40 views

Gravitational force acting on two particles

According to Newton's Laws of Gravitation, $F=Gm_1 m_2/r^2$ So gravitational force F is directly proportional to $1/r^2$. Now if we consider 2 point masses in vacuum at rest at a distance 'd' ...
4
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3answers
720 views

How far up an object is its gravitational potential energy taken from? [on hold]

This is quite a brief question but, Is the $h$ value in $mgh$ taken from an object's base, middle of top. For example, if a person was $1.5m$ in height and they were standing on a hill of height ...
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3answers
75 views

Is gravity actually missing or lower in certain spots on Earth?

I have heard and read about "missing gravity" in some regions of Earth. What I seemed to gather from this info is that if I go to a certain spot and jump, I can jump higher; or I could maybe lift more ...
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1answer
63 views

Clarification of the physics involved of an orbiting body in a circular orbit

I am writing a physics simulation program to simulate a body orbiting a planet but I am a little confused about the physics involved and would like some clarification. To simulate gravity I am using ...
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0answers
15 views

Misbehaving singular isothermal sphere potential

The singular isothermal sphere (SIS) is a useful simple model often used in astrophysics. It has density profile: $$\rho(r) = \frac{\rho_0 r_0^2}{r^2}$$ This is well known to have some quirks ...
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2answers
62 views

Where to use acceleration due to gravity $g\propto\frac{1}{r^2}$

I (and we all) know that acceleration due to gravity $g\propto\frac{1}{r^2}$.Now my question is can I use this for depth.If not,why?If we can use it for depth or not struck me when I was trying to ...
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4answers
99 views

Does a flying bullet get KE from gravity?

A projectile P is shot horizontally at 9.8 m/s from a height of 4.9 m, considering no air friction, after a second it will have v = 9.8 m/s on the x-axis and v = -9.8 on the y-axis. Because of ...
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2answers
66 views

Dimensional analysis - When can you introduce constants that make dimensions compatible?

I have just read this question: What justifies dimensional analysis. One statement was: Maybe the speed of a comet is given by its period multiplied by its mass. Why not? As a formula this is ...
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1answer
56 views

Can 4 collinear planets exist?

Imagine 4 planets, A has moon a and B has moon b. A and B are binary planets. Is it possible that a and b and A + B all have same the period, so that the 4 planets are collinear?
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1answer
49 views

How is the value of Standard gravitational parameter for Earth derived?

Its been a while since I've done any physics, I'm working on some orbital programs. I'm using this formula $\mu = MG$ where $M$ is the mass of the body and $G$ is the gravitational constant. The ...
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1answer
35 views

Gravitational intensity [closed]

I calculated the gravitational intensity and potential at a point P due to a horizontal linear mass distribution of length '$L$', mass '$M$' and uniform linear density at a distance '$R$' apart from ...
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3answers
252 views

Fundamental paradox with Newton's Law of Gravity?

This is my first post here, but I've been struggling with this problem in my head since I studied physics at school when I was 14 (30 years ago!). There seems to be a fundamental paradox with ...
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0answers
18 views

Eccentricity of planetary orbits: What information is contained?

I'm having a little trouble understanding what makes a planetary orbit explicitly elliptical. Is it simply that the initial velocity was different from the circular orbit case for a given starting ...
2
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1answer
40 views

How does the strength of gravity affect human walking speed? [closed]

Walking requires friction and gravity, would humans be able to walk faster in different strength gravitational field than that of earth's? What strength of gravity would allow an average human to ...
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2answers
55 views

Gravity Vs Distance [closed]

What is the relationship between the magnitude of earth's gravity and the distance away from the earth's surface? Or at what rate does gravity decrease as one moves away from earth?
4
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1answer
55 views

How “large” is a Lagrange point?

When placing an object at a L-point, the natural assumption, as with all things gravity, is that you needn't place it in an exact spot to achieve a stable configuration. How much room do you have to ...
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2answers
49 views

With friction, does the path followed from A to B affect energy transfer?

Consider I have a roller coaster that can travel across one of three paths, all of which are half circles of the same size. The half circle is an arch that starts vertically up, and ends vertically ...
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0answers
23 views

What is the time of flight of a projectile with variable acceleration? [duplicate]

I recently solved a problem involving the maximum height of a projectile launched at a high speed. For example, an object shot straight up at $10.4\ km/s$ (an arbitrary number slightly less than ...
1
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2answers
54 views

Guidelines for $n$-body problem inital conditions

I'm trying to solve a 5-body problem (for the sake of the argument it can be any given $n$) numerically, yet every initial condition I choose seems to eventually drive the bodies apart to infinity or ...
2
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5answers
144 views

No need Power to fly ? Paradox [duplicate]

I would like to know how much power I need for magnetic levitation. $$P = Fv.$$ $F = F_g \approx \text{mass} \times 10$, okay. But $v = 0$! I can't believe I need no power to keep an object in the ...
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2answers
35 views

When drying paint brushes washed with water, which way is the best to orient them?

After washing my paint brushes with soap and water and rinsing them, in order to avoid damage to the bristles and the ferrules and the wooden handle, is it best to hang them bristles down and let ...
0
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0answers
9 views

The ratio of equators radiuse to polar radius

I want to calculate (Re/Rp) where (Re) is the rediuse of earth in the equator and (Rp) is the rediuse of earth in poles. I want to use newtons laws, the eqution of gravity and centripetal force ...
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1answer
63 views

How are tidal gravity and curvature related?

I see tidal gravity mentioned in the literature sometimes, and sometimes people even say something like that is the “real gravity”. I am confused about the significance of tidal gravity, and what ...
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4answers
162 views

How far apart do two objects have to be for there to be negligible force between them?

Inspired from the commentary on this question. How far apart do two objects have to be for the gravitational force between them to be negligible? By negligible I mean, that it could never be ...
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0answers
52 views

Why value of $g$ is 0 at the centre of the Earth? [duplicate]

My question is simple, why the value of $g$ is 0 at the core of the earth? Being the device for attracting all the objects over earth, why the value becomes nullified over itself? It should be maximum ...
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3answers
74 views

Can Gravitational force between two bodies always produce motion?

Imagine there are two bodies of mass 1 Kg each separated by some distance.Then by Newton's formula of calculating gravitational force we can see that the gravitational force between them is very ...
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1answer
90 views

What would be gravity in one spatial dimension? [duplicate]

First of all, I should say that I understand if this is put on hold for being unclear... but I'll try my best to make it as clear as it can get. For all the time I spent learning Newtonian Gravity ...
2
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2answers
80 views

Reaction due to gravity

There is a reaction to the gravity of the earth on us but the earth does not move due to its huge mass. But what if I combine the weight of all humans and other things on Earth? Is it not enough to ...
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0answers
45 views

Do I weigh less during high tide? [duplicate]

Given weight = mass * gravity do I weight less during high tide and more when tide recedes? My guess is weight = mass * gravity * gravitational pull of moon factor
1
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1answer
105 views

Why doesn't the moon crash into the Earth?

I was searching about 'why do not moon crash to earth due to its gravity?'Then by reading physics stake exchange existing questions I came to know that its the sideways motion of the moon that keeps ...
4
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3answers
111 views

Tidal Forces Misunderstanding [duplicate]

I'm sure there are several misconceptions here and I'd greatly appreciate it if someone could help me identify and correct them. When calculating tidal forces across an object, the earth for example, ...
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1answer
30 views

Advent of our solar system

When the solar system was born why did Sun not consume all the planets by its immense gravity, as the planets were all gases, so it would have been very easy?
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2answers
55 views

If planet orbits are in the shape of an ellipse and the sun is a focus, where and what is the focus? [duplicate]

I've studied ellipses. I've studied physics. But when it comes down to the elliptical orbits of the planets is where I get confused. Ellipses contain two foci — and in the orbits of our solar system ...
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1answer
83 views

Acceleration orthogonal to movement direction

I've been told that acceleration orthogonal to an objects movement direction doesn't require energy. Thus when a satellite goes around the earth, the change in direction caused by gravity doesn't use ...
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1answer
96 views

Does Earth get gravity due to it's spinning? [duplicate]

Consider my example below. Example: 1. A man standing on grass(point) on earth surface. 2. He jumped. 3. And returned back, and he could find the same grass(point) under his foots. Right? If earth is ...
2
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3answers
95 views

Solving the two body problem numerically

I'm trying to solve the two body problem numerically, setting up $G$, $m1$ and $m2$ to be equal to 1. then I located each mass on positions -5 and 5 respectively along the $x$ axis and gave them both ...
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3answers
157 views

Infinite acceleration

Let's say we have two planets at a stand still within reasonable distance of each other. They will accelerate towards each other and subsequently collide. If instead we give them a sufficient (but ...
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4answers
89 views

Reduced-gravity flight (A300 0-G): what is actually reduced?

I doubt I can hide from the effects of gravity when I'm close to Earth. We usually don't question this biker is fully experimenting gravity: Source. But with the well-known "reduced gravity" ...
2
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2answers
51 views

Will the gravitational pull of air affect the falling rate of an object?

After looking at this question: Don't heavier objects actually fall faster because they exert their own gravity? A thought occurred to me that due to the increased gravitational pull of the ...
0
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1answer
34 views

Slingshot Energy into traveled distance [closed]

If I have a slingshot and I am told that when pulled it has about $E$ joules of energy, how do I compute the height at which an object of mass $m$ would travel if the slingshot is released in the ...
5
votes
3answers
278 views

Is it true that spring has more force acting on it at its positive maximum amplitude than than at the negative one?

Am I missing something? It seems obvious to me that at $+A$ and $-A$, the spring has restorative forces equal in magnitude but opposite in direction. But since gravity is always pulling it down, ...
1
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1answer
33 views

Gravity's tall box with a ball inside - scenario

Let's imagine we put a ball inside a box such that it doesn't touch its walls, and suddenly drop the box. Because the two objects fall at the same rate of acceleration, the ball will stay at the same ...
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3answers
65 views

What is the definition of potential energy? [duplicate]

I have problems with this equation: $$U_G ~=~ G\frac{m_1m_2}{r}.$$ It's for potential energy of say something placed on Earth. But it intrigues me. $r$ is the distance from the very center of the ...
0
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1answer
44 views

When will a ball running between two downwards slopes stop going back and forth?

Two angles $a$ and $b$ meet at a point, making an angle $c$ between them. $a$ and $b$ are all $0 < \theta < π/2$. $c$ is $π/2 < \theta < π$ $a$ is to the left and opens to the left, $b$ ...
10
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3answers
766 views

Can a building get taller at night?

UberFacts recently tweeted "Office buildings are taller at night—a 1,300-foot-tall skyscraper shrinks about 1.5 millimeters under the weight of 50,000 occupants." Is what they are saying valid? It ...
2
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1answer
98 views

How does a planet's size really affect its surface gravity?

If we located an exoplanet whose diameter was $x$ times that of the Earth's in size, and which for simplicity appeared to have an identical composition to that of Earth, then its mass might be taken ...
1
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2answers
56 views

Gravity underground on the moon?

They say that gravity Decreases as we dig into the earth. But I also read that gravity increases for the first approx. 2000km of distance underground. Using this rational, could we dig about 200 to ...
1
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1answer
129 views

Why are tidal forces pointing away from the Moon? [duplicate]

I am currently reading The Science of Insterstellar, which explains most things very well, but some things leave me confuzzled, which I hope to get answers to here. I am no physicist, but highly ...
0
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1answer
32 views

What velocity do I need to get the moons orbit perfectly aligned with the earths center [closed]

I have a simulation for universal gravity with two objects. How can I calculate the velocity or instantaneous force I would need to apply to object 2 (the moon) to get it to orbit so that the origin ...