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

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Find the center of gravity of a system with three spheres [closed]

Three spheres are put on a table. The first sphere, whose mass is 1 kg is 20 cm away from the second whose mass is 2 kg and the third sphere is 100 cm away from the first sphere and has a mass of 5 ...
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1answer
35 views

How to Model Differential Gravitational Field from Vectors?

The tides are caused by differences in the gravitational field of the moon on the near side and far side of the earth. If I set this gravitational field as a vector field using Newton's Law of ...
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4answers
81 views

Is the mathematics in my answer valid? (C is the right answer) [closed]

I have a good understanding of the concepts at hand, but I'm not so good at the mathematics part. I know the answer already (C), but would like to understand the mathematical way of determining it. ...
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1answer
66 views

Wouldn't dark matter throw off the calculation of Earth's 'light' mass and estimates of its composition?

The Cavendish experiment first determined the mass of the Earth and (arguably) the gravitational constant. However, given the ubiquitous nature of dark matter, it seems reasonable that at least some ...
2
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0answers
21 views

Orbits of binary pulsars. How to calculate? [duplicate]

If I may ask: How can the orbits of binary pulsar stars, with similar mass, be calculated from Kepler's laws? Considering that both large central masses must be located at their mutual foci. Also, how ...
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2answers
69 views

Can $F=ma$ be used to calculate ground reaction force of someone walking/running?

Can Newton's second law of motion $F=ma$ be used to calculate ground reaction force of someone walking/running?
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3answers
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Why does weight affect acceleration with gravity

I'm sure this question has been asked before, but my question is different, because it can't be answered with some formulae. My question is, why do heavier objects decelerate faster when moving away ...
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2answers
102 views

General Relativity view of Newton's apple

If one considers the free fall of an object of mass $m$ from a hight $h$ in the Earth's gravitational field (neglecting air friction) from the point of view of GR, what would be the main corrections ...
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1answer
47 views

Where do we get the terms involving $\Phi$ in parentheses come from in the static weak field metric?

I am confused about the static weak field metric. As written in Hartle, it reads \begin{equation} ds^2 =-\left(1+\frac{2\Phi(x^i)}{c^2}\right)(cdt)^2 +\left(1-\frac{2\Phi(x^i)}{c^2}\right)(dx^2+dy^2 ...
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1answer
62 views

What force acts on a coin that has been tossed when it is half way to the top? and what force acts on it when it is at the top?

This is a homework question and it appears to be a misleading question. I think that the answer is gravity for both of them. The only alternative answer I have is kinetic energy half way up and ...
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3answers
394 views

Forces on a ball thrown upwards

When a ball is thrown up in upward direction, it is said that force is in downward direction. Why we don't we consider the force given to the ball to throw up in the upward direction? Is there is no ...
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1answer
42 views

Decreased velocity away from gravity

Say I have a particle ($G$), which has the mass of the earth (hypothetically), and I have a second particle ($P$) moving away from $G$, in a line that is not parallel to the earth. Would this line ...
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1answer
43 views

Create a star system fit to conic equation

For simulation purposes, I'm trying to create a binary star system. If I have a conic equation such as $ax^2 + by^2 = c$, and the masses of two stars, how would I find the $x$- and $y$- velocity ...
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1answer
39 views

Tidal tails of galaxies after collision

When there is a collision of 2 disc shaped galaxies, there is a tail formation created from both the galaxies. I read here that this was due to tidal forces, but I couldn't figure out how this ...
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0answers
22 views

Why does the Moon not rotate about its axis, relative to Earth's rotation [duplicate]

One of the common features of the Moon is the fact that only one face of the Moon is ever visible from Earth, regardless of how much of its orbit the moon has made about the Earth. This would imply ...
0
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1answer
48 views

The stronger the gravity, the faster an object will fall? [closed]

On a planet with gravitation ten times stronger than that of Earth's, will an object fall faster? Let's suppose that there are two planets; Roddo and Earth, respectively. Roddo has ten times the ...
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2answers
45 views

How did the planets (in the Solar System) start to revolve around the sun if they were attracted towards the Sun via the gravitational force? [duplicate]

The planets in the Solar System revolve around the Sun in almost circular paths called orbits. The Sun pulls the planets with the gravitational force,but the planets do not get drawn to the Sun but ...
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3answers
107 views
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3answers
157 views

Does the Earth revolve around the Sun?

I am aware of this Phys.SE question: Why do we say that the earth moves around the sun? but I don't think this is a duplicate. In a binary star system, where the masses of the 2 stars are not so ...
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1answer
74 views

Do we need Escape Velocity [duplicate]

This may seem silly a lot but I really need some clarification on the necessity of escape velocity for a rocket leaving the Earth's gravity. A stone thrown vertically upwards reaches to a certain ...
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2answers
68 views

Does the gravitational force of a massive, spherical body draw only towards its center of gravity, and to no other area?

Consider the premise that at the center of Earth (for example) an object would be weightless because of the relatively even distribution of mass surrounding it, and the resulting gravitational pull on ...
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2answers
71 views

Orbital Velocity Question

I have a satellite in a stable trajectory around Earth, of a Mass $m$. I know that its velocity is: $$ v = \sqrt{mG/r}\, $$ But now it begins accelerating directly against the gravity vector (i.e. ...
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1answer
64 views

How do you calculate density if you also account for gravity?

Consider this. I have an Earth-sized quantity of water that I throw into space. Naturally, it will assume the shape of a ball. Now hear me out. Density's definition generally assumes that it will ...
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1answer
94 views

How did special relativity change physicists views on the two prominent inverse square laws (ie Newton grav and Coulomb's law)?

On page 107 in Hartle's Gravity -- An introduction to Einstein's General Relativity, he says the following With the success of special relativity it became apparent that the Newtonian theory of ...
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2answers
103 views

Would it be possible to make a space elevator only in the atmosphere?

I wonder if with current day technology we could make a "floating platform" which hangs from a satellite by a space elevator. This could allow a "launch process" involving floating a balloon to the ...
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4answers
149 views

How would swimming in low gravity work?

Sorry I know very little of actual physics, I'm not looking for hard and fast numbers just a general idea of how the mechanics would work. For the sake of argument, say you were on a planet or moon ...
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1answer
47 views

Can small chunks of cosmic matter revolve around artificial satellites in space?

I have always studied that where there is a body with mass, there is gravitational pull. So can small chunks (or dust) of cosmic matter revolve around artificial satellites in space? Or rather are ...
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1answer
83 views

Why does the gravitation potential in a uniform field have negative values?

As we know the gravitational potential is the work done per unit mass in taking a point mass from zero potential (at infinity distance) to a point in a gravitational field. But why is the work ...
2
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1answer
45 views

Computing the gravitational force on a planet in a particular system [closed]

I have a system of four planets moving in a 2D plane. I'm trying to write some code (C++) to find the positions of these planets at time t=3. I'm probably going to attempt this via a leapfrog ...
2
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1answer
181 views

If a bullet is fired vertically upwards, when it comes back does it fall to the same spot?

What I'm basically asking is that if a body is projected with sufficiently high velocity so that it doesn't escape from the earth's gravitational field but reaches an appreciable height with respect ...
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2answers
105 views

Problem with an exercise: position and velocity of a thrown sphere with non uniform acceleration

You stand at the earth's surface, have an object, for example a sphere, of mass $ m_1 $ and throw it with a velocity $ v_1 $ into the atmosphere, perpendicular to the surface. Let $g$ at the surface ...
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1answer
311 views
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1answer
62 views

What physics concepts support the observation of the book and paper falling together?

you place a sheet of paper on a book, it falls with it rather than being separated & slowed by air resistance. What physics concepts support the observation of the book and paper falling together? ...
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2answers
287 views

Why are heavy things harder to lift?

According to multiple websites, any object in free-fall (no air resistance) on earth will accelerate towards the Earth at 9.8 m/s. If all objects fall towards the Earth at the same rate, regardless of ...
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1answer
82 views

How can we prove simply that acceleration for every freely falling body is equal to $g$? [duplicate]

If I allow two bodies of different masses to fall freely from same height towards the earth, how can I prove that the acceleration produced in both was constant and equal to gravity.
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2answers
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Will an object falling into Earth's orbit start spinning?

Assume an object falls towards Earth (I've drawn a hyperbolic orbit, but this would apply to any orbit). The object starts at $A$, and at this point it is not rotating i.e. an observer on the object ...
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1answer
39 views

Do all thing move against gravity with -9.8 meter per second squared acceleration?

If I throw a ball to height h above the earth's surface and then shoot a bullet that reaches the same height but would there be same quantity of acceleration produced in both?
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2answers
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What is the meaning of the negative sign in $W = -\Delta U$?

What is the meaning of the negative sign in $W = -\Delta U$ ? As far as I understand, $W = -\Delta U = -(U_f - U_i) = U_i - U_f$. While $U_i$ is the initial potential energy (before applying the ...
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0answers
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Differential Equations for Two-Dimensional N-Body Simulation

So I recently asked a question about improving the stability of a two-dimensional orbital simulation (as before I was using Euler integration). I was told to use Runge-Kutta 4 for a more stable ...
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0answers
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How much time would it take for a free-falling ghost-like object to cross the entire Earth? [duplicate]

We have an object of mass $m$ which can go through matter like a ghost. It's only affected by gravity, not by any other force, so it's in free fall. At the instant $t=0$ it is at the surface of the ...
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6answers
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If the gravity at the center of the Earth is zero, why are heavy elements like iron there?

If gravity is zero at the center of the earth, why is there a core of heavy elements, such as iron? Alternate question for the opposite hypothesis: If gravity is greatest at the center of the ...
2
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2answers
70 views

Air Drag in orbit

Artificial satellites don't orbit the earth forever. Eventually the Earth's atmosphere, thin as it may be up there, will bring them down. But did you know the linear speed of a satellite in a near ...
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0answers
24 views

weightlessness and forces conceptional question

I am currently learning about forces and newton's laws of motion. I have a question in my book which I don't understand though... Here it is: (note: I dont want the answer I just want to understand ...
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1answer
90 views

Motion in the gravitational field along a trajectory [closed]

A point particle of mass $m$ is moving in the gravitational field along some trajectory which is described by the function $y=y(x)$, which is in a vertical plane and is continuous. Initial ...
0
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1answer
71 views

Two body problem with given start positions and velocities [duplicate]

I am trying to program a $n$-body problem simulation. To calculate the position and velocity after a time-step I want to split it in multiple 2 body problems. Now I am stuck, trying to find the ...
2
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1answer
33 views

Coexistence at Lagrange points

I was wondering how precise the location of an object in a Lagrange point needs to be to maintain stability, since it seems that several natural objects (asteroids) exists together in some of these ...
0
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1answer
108 views

Prove that orbits are conic sections

How does one prove that an orbit of a satellite around a planet of significantly greater mass than the satellite is a conic section (i.e. an ellipse, circle, hyperbola, or parabola)? Also, there is ...
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1answer
52 views

Minimum Distance for “Speed of Light Approach”

I tried to calculate the minimum distance between a planet and a test mass for the mass to attain the speed of light on colliding with the planet's surface if it were released from rest at the initial ...
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1answer
404 views

Pressure and Tall Buildings

Does living in tall buildings somehow exert more pressure on our bodies? I remember reading something about this once but I'm not sure if its true.
3
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1answer
77 views

Calculating a two-dimensional orbital path with infinite granularity (non-Euler integration)

For a game I am making, I am trying to calculate the position of an orbiting object around one or more bodies. I have successfully implemented this gravity simulation by calculating the force, then ...