# Tagged Questions

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

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### Trying to understand Newtonian limit of GR

First ever post - please be kind. I'm trying to understand how General Relativity becomes equivalent to Newton's laws of motion, plus Newton's law of gravitational attraction in the limiting case of ...
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### falling in a gravitional field [duplicate]

It is often stated that masses fall at the same rate towards the Earth at the same rate (barring things like friction), and this seems to be quoted as the Equivalence Principle. Is this statement ...
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### Velocity Related To Gravitation [closed]

Which Equation is correct $v^2=\large{\frac{2GM}r}$ OR $v^2=\large{\frac{GM}r}$? I am getting confused here.
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### Why did Trebuchet have so long throwing arms?

Have a look at such an historical Trebuchet: As you can see, the throwing arm (left) is much longer than the weight arm (right). Law of conservation of energy says, potential energy from the ...
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### Use equations to create a realistic problem [closed]

Given the following equations: $100$ m = $0$ m + ($50 \cos\theta$ m/s)$t_1$ $0$ m = $0$ m + ($50 \sin\theta$ m/s)$t_1$ - $\frac{1}{2}(9.80$ m/s2$) t_1^2$ I am supposed to make up/create a real-life ...
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### About the use of Newtonian Relations for the movement of stars in the Galaxy [duplicate]

From a General Relativity point of view Gravity is given as the result of spacetime curvature interacting with energy-mass density. To get to the Newtonian limit one needs to take a) Non-...
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### How is the centrifugal force responsible for Earth's oblateness? [duplicate]

I'm having serious problems understanding the centrifugal force caused by Earth's rotation. How does it affect the Earth's shape? Should I draw the gravitational acceleration (the one in Newton's ...
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### Gravitational acceleration of asteroids [closed]

If an asteroid is moving through space at a speed that exceeds escape velocity of the earth and that asteroid is on a collision course with the earth will the asteroid Accelerate as it falls into the ...
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### Finding an object's final velocity with distance dependant force [duplicate]

I am (just for fun) trying to calculate the velocity with which the moon would impact the earth if it stopped orbiting and simply headed towards earth. I know the force is $\frac{G m_1 m_2}{r^2}$. ...
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### Need motion equations for falling ball for simulating [closed]

I am currently M.S student in artificial intelligence(A.I) and working on my thesis on reinforcement learning, which robot should learn by itself how to control a quadcopter. Long story short, I have ...
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### Why the pressure in liquids only depends on the height?

look at this picture : and also look at this one: imagine that the surface area of both is the same and both of them are full of water. My question is that why they both are pressing the beneath ...
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### Will centre of gravity coincide with centre of mass if density of object is non uniform?

I read that for bodies of very large dimensions, but having non-uniform density, the centre of gravity does not coincide with centre of mass. I can understand that with large dimensions the strength ...
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### Why doesn't orbital body keep going faster and faster? [duplicate]

If we consider the change in velocity during an infinitesimal interval of an orbit: where body B is orbiting body A, we can see that the magnitude of the resultant vector (the green arrow) is ...
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### Why is the gravitational constant so difficult to measure?

The gravitational constant seems to be very low precision. For example, in the Wikipedia article recent measurements are given as having the significands of 6.67 and 6.69, a difference of 2 parts in ...
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### What is exact difference between gravitational force and magnetic force? [closed]

I've read that gravitational force is due to mass only and magnetic field is due to moving charged particles. But my question is: what are other difference between them? Can we set up a small ...
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### What factors will make Earth re-rotate again if it stopped? [closed]

"What will happen if Earth stopped rotating?" have been answered multiple times with a lot of informative and interesting answers. Continuing this hypothetical question, I have another one in mind. ...
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### How does Modified Newtonian Dynamics (MOND) violate Newton's laws?

I have read some articles on MOND which indicate that a modification of gravity violate Newton's third law, but I don't know how exactly that works. I do know that if Newtonian acceleration is smaller ...
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### If we threw a baseball from the ISS, could we deorbit the ball?

Clearly this is a hypothetical question. Say we bring a star baseball player into NASA, prep them appropriately for a mission in space, and fly them up to the International Space Station. They go on ...
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### Calculate the speed of Halley's comet at his perihelion [closed]

Knowing that Halley's comet orbita the sun every 75,3 years, that the semi-major axes is 17.83 AU, the semi-major axes is 4.53 AU and at his perihelion he is 0.586 AU away from the sun. With these ...
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### How would I find the velocity of an object after it doesn't fully enter the gravitational pull of a planet and is kind sling shot out of its gravity?

Obviously that question doesn't have a lot of jargon having to do with math and physics. I am not a physicist, I'm not a mathematician, I'm trying to make a game and simulate some physics found in ...
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### Does the human body have a measurable gravitational field?

I am researching communication other than speech or vision. The human body emits radiation in the form of heat; As the body has mass, will it have a gravitational field?
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### Moment of inertia and gravity

Would the objects have moment of Inertia if there was no gravity? Because imagine a bar, if I put my hand at the center of the bar and rotate it, it would be easier than rotate the bar picking one ...
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### Free fall in non-uniform field

Imagine I'm a space-diver, with mass $m_1$, 500 miles above the Earth's surface at $x_i$. I want to calculate my position, velocity, and acceleration as a function of time, accounting for the Earth's ...
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### Do all objects free fall at the same rate regardless of their mass? [duplicate]

Is it true that all object will fall at the same speed in vacuum irrespective of their mass because the acceleration due to gravity of Earth is 9.8 m/s2. Then what happens to the gravitational force ...
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### If gravity on a non-rotating body suddenly stopped, would an object on the surface fly away? [closed]

This is a very trivial question, and I tried to word the title as concisely as possible, but I can't seem to figure it out. This is not referring to any hypothetical discussions regarding Earth. ...
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### Do greater mass objects attract objects quicker, than lessor mass objects? [duplicate]

If I jumped up and down on the moon it would take longer than if I jumped up and down on earth... the only changing variable being mass - the difference in mass between the earth and moon. wouldn't ...
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### Will the distance still be measured from the centre? ( During gravity measurements)

I have read that to find the gravitational force between two objects, we need to have the distance between their centres. Now if i have an object whose centre is not on it’s body ( as in a ring ), ...
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### Dynamics of pairwise distances in the $n$-body problem

Consider the $n$-body problem where we are interested in describing the time evolution of $n$ masses interacting through a potential $U$. Let $D$ be the matrix containing all pairwise distances ...
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### Relationship Gravitational Potential and the Tangential Velocity of a Satellite

So gravitational potential is given by $V(r)={\frac{GM}{r}}$ and the tangential velocity of a satellite is the square root of $V$, i.e. $\sqrt V$. So how do these two relate, if at all?
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### Finding mass with an estimated gravitational force

As asteroids orbit the sun, they experience gravitational force exerted on them by the sun, and they in turn exert a very minute force back on the sun. Because of their small size, asteroids don't tug ...
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### Vector interpretation of Kepler's 2nd law ( r X a = 0 )

I just read the vector interpretation of Kepler's second law and the conclusion put me in a confusion. The interpretation concludes by demonstrating that r X a = 0, where boldfaced r and a are ...
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### How to calculate projectile path having starting and end point?

I want to show a projectile path between two points (x1,y1) (x2,y2 ) on graph. Here I know two points, start point and end point. I tried solving by taking launch angle as 45 degree, it doesn't seem ...
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### Why are objects (such as planets) in motion and not static? [duplicate]

I am just curious, why are all the planets, rocks etc in motion? Would they fall into objects with larger gravity if they were not in motion? What is stopping the earth from falling into the sun or ...
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### Is there any experimental evidence to distinguish the total gravitational force exerted by the two proton and a helium nucleus?

I know that the sum of the mass of the two proton is greater than the mass of a helium nucleus (two proton). As the mass different is transformed into energy by the Einstein mass energy-equivalence. ...
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### Can I re-wind gravity?

Suppose I perform an arbitrary simulation where I integrate the motions of a collection of particles which interact only gravitationally. Suppose I use a time reversible integrator (to be specific, ...
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### What is the gravitational field lines pattern of a sphere of mass $m_1$ in an open ended box of mass $m_2$?

This Quetsion is inspired by this Fig of a positively charged metal sphere in an earthed metal box:
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### Why is there no negative mass? [duplicate]

We know that the entire matter has a property called mass. Charge is also a property of matter. If negative charge can exist, why don't negative mass exist? Also, like charges repel each other. Then ...
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Why is graviton not found yet? Newton said gravity pulls us, Einstein said space is bent and it pushes us, hawking predicts the existence of graviton and 'hawking radiation'. How far are we from ...
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### Energy diagram of a planet with fixed mechanical energy

Consider the following energy diagram for the motion of a planet about a star. The centrifugal potential curve can be represented once I fixed the angular momentum $\vec{L}$ of the planet. To fix the ...
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### Climbing Stairs and Calories Burnt

I climb stairs to work (20 floors) every day . The least amount of work my body is doing by gaining potential energy (P.E) = mgh where m is mass , g is acc. due to gravity and h is height . Assuming ...
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### Orbiting in space (free fall) and centripetal force?

So basically astronauts are weightless b/c they are free falling. But to get to that state they need to be moving real fast. So why doesn't that speed along with the centripetal force affect them? I ...
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### Question related to accleration due to gravity [closed]

What effect will be seen on the value of accleration due to gravity if radius of the earth is decreased keeping the mass constant?
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### Stars more affected by gravity of stars further away, need help understanding argument why

In the first chapter of Binney and Tremaine's "Galactic Dynamics" there is a statement that I don't yet understand. The first chapter of the book is linked here, straight from the publisher. The ...
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### Why it's more difficult to walk in an inclined plane than in a causal road [closed]

my question is about something very casual , but when i tried to solve that , it was not easy at all . My question is : "Why when we walk in an inclined plane we get tired more than when we walk in ...
I don't understand why the conservation of angular momentum can imply an acceleration, in absence of a force. Consider for istance planetary motion. The angular momentum $\vec{L}$ of the planets is ...
I am just a beginner in dimensional analysis, and I see that $G$, the universal gravitational constant, is independent of everything. Speed, for example, depends on distance and time, but $G$ does not ...